Okay guys, need some help with some repowering thoughts
January 27 2006 at 7:47 AM
Dave Mehl (no login)
I am running the 275-hp Lincoln motors in my early model Commander 38, and they're well oiled, tuned, and run reasonably well, but I know the resale value of the boat is low with these motors, and I have been considering a repower in the future for a couple of reasons.
I want to keep the boat because I have so much time getting everything the way I want it. The cabin is neat and clean, and we generally love the boat.
In the future we know we'll have to eventually sell the boat due to our age and health issues. I know during the next ten years, I'll probably be faced with some kind of a rebuild or repower with these old engines, and I am considering a pre-emptive repowering before they force me to do it on their schedule.
Now before everyone jumps my case, please listen to my reasons for thining about small blocks in this boat. I like the thought of using small blocks because parts are plentiful, and they can be considered almost consumable. I can get a replacement short or long block for next to nothing, so I wouldn't be afraid to run those small motors hard if I wanted to. The cost of these motors is very attractive. The smaller motors would fit into the Commander hull with a huge amount of room to spare. I can still get 250 to 275-hp from them, at less torque, but fuel consumption could be an issue in the future too, as oil prices continue to climb.
So here is my thinking, I'm considering small block (Chevrolet) power in the boat, a pair of 350 GM marine motors with marine cams and 4-bolt mains of course for maximum torque, and new transmissions to go with them. My Lincolns have parts that are very hard to find these days, and the small block chevy motors have a parts availability that is just unmatched.
If I do this I suspect I can retain the same 1-3/8" shafts but may have to change out the props. Speed is not an issue with us, as we almost never ever run the boat at maximum throttle, as this just isn't our style of boating, and all it does is consume huge amounts of fuel and run the risk of damaging the motors.
Thoughts please, including the potential resale of the boat with small block motors in it. Would a potential buyer look favorably on "new GM 350s" or would he run for cover?
Just getting ready to head out to lunch and saw your note.
Interesting concept you have there. I'm probably not the best guy to discuss this one with, as I'm probably one to suggest the biggest gas motor you can get on the boat!
I do believe the 38 Commander was initially offered with small block power, but back when they did it, it was probably the 327-F, which was rated at 210-hp each. Nowadays you can get a 4-bolt 350 that can produce around 300-hp in pretty reliable marine form, but I'll have to look up the torque figures to see how that works too. If you judge performance on "horsepower alone", then technically the small motors at 300 hp should be able to make the boat go as fast as the big motors at 300-hp can do. I have a lot of speed formulas for boats and they're all based on horsepower, and they do not recognize torque, but I know torque on a boat will make a big difference on the "work" the little motors will have to absorb.
If you don't do planing speeds often, they might just survive, but how long they'll survive is the question. A 4-bolt small block has good bearing strength, and again, I'll have to look at the crank throw on those motors to further evaluate how hard the motor is really working.
One thing for sure, a pair of small blocks in my engine compartment, would look kind of lonely down there, compared to the big wide 427 Fords that are down there now, and I suspect your big "MEL" motors are equqally huge (or even larger).
I want to take a look at the power and speed data Bill posted the other evening too, because I think that data is based on some similar weight factors and power factors too.
I see a lot of good posts this evening, but I want to respond to this one.
Dave, there is a lot of precedence at CC for putting the small motor in boats bigger than yours.
Here are a few examples, doing just a quick look.
The 1963 and 1964 42-foot wood Constellation (being sold along side the Commander) was offered with twin 283 motors, and they were rated at 185 hp each, while the boat weighed in at 21,000 to 23,000 pounds. Performance figures for that boat should be available. Chances are good your Commander doesn't weigh that much, nor would it have as much hull drag, and the small blocks of today have a lot more power.
The 1972 42=foot wood Constellation was offered with twin 350Q motors, also being sold along side the fiberglass Commander. It weighed in at ariybd 21,000 pounds, which is also heavier than your Commander.
The 1962 42-foot wood lapstrake Corinthian was offered with twin 283 motors, and it weighed in at around 21,500 pounds.
I am not sure Paul is correct in his comment about the 38 Commander being originally offered with 327 power, and I'm interested in knowing where he got the info, since the Mariners Museum doesn't have this comment in their 38 Commander file (that I can see).
In any case, there is a lot of precendence for boats weighing a lot more than yours, with motors a lot less capable than the modern day 350 marine motors, many of which produce 270 or more horsepower all day long.
Therefore I would say your approach is not only "viable", I'd say it makes a lot of sense "if" you are planning on using your boat for "day cruising" and not long distance sport fishing or long distance cruising. Even then, I think today's small block motors with the peoper gearing and props would do well.
I thought the 38 Commander was originally offered with small block power
January 28 2006, 6:18 AM
I distinctly remember hearing or reading that somewhere, and I'll try to back it up now that you've commented on it. I looked in the Essential Guide, and you're right, it does not show up in the book.
If you've ever tried to track engine development at FoMoCo, you'll know they did a lot of things that never made it to the paper trail, and also they destroyed a lot of records they thought were old and obsolete. Therefore, I would not consider the CC records to be "totally accurate", but most likely they are on this one.
If I find anything to back up the issue, I'll be sure and post it.
My 1967 Chris-Craft brochures show the 38' Commander, 38' Commander Sedan, and 38' Commander Sport Fisherman available with "Twin 210-hp or 300-hp V8's or 258-hp diesels.
But you guys are missing the whole point - today's "small blocks" are a lot different than those in the 60's and 70's.
here is a not very good scan of a 1967 Chris-Craft brochure showing three 38' Commander models with the avilable 210-hp and 300-hp V8's, and the 258-hp diesel.
That's "the proof" I was looking for (SBC in the 38 Commander)
January 28 2006, 12:12 PM
Good find!
I rest my case, about the "accuracy of the so-called industry bibles" including the Essential Guide, because the Guide obviously missed this one by a country mile!
I know for a fact that there are numerous versions of the SBC and BBC, and that Crusader for instance, has a reputation for buying the 4-bolt truck blocks, and Mercruiser had been using the 2-bolt motors for higher power ratings, and that seems backwards but that's what was going on. Don't know now what they're doing. Same with the SBC, you can get a "crate motor" and it is gauranteed to come on a crate, and that's about all. Those could be two bolt taxi motors, and certainly not the 4-bolt truck blocks that would be ideal for marine use.
the SBC (small block Chevrolet) certainly has been developed over the years. You can even get a 400 cubic inch small block and I believe those have siamesed cylinders (as do NASCAR motors). In any case a 350 4-bolt would appear to be "the choice" in Crusader form, if I were on the hunt for a smaller alternative to the big Ford or Lincoln. I dare say the newer motors with almost the power of a "detuned" 427 would make for a pretty good speed, but naturally those motors would never stand up over the years if pitted against a 427. In any case, for Dave, it may make sense to do the conversion, enjoy the boat, and then end up with something that may still be marketable when you plan to sell.
This is just great. I'm amazed, Bill thanks so much for that marketing sheet, it did wonders for me. It took away a lot of doubt. Yes, I know the original small motors were probably slow, but I think I can easily get substantial more power from the larger (350 series) and still not be overtaxing the motor. I'm going to assume CC used the same gear ratios (2-1/2 to 1) for the small motors too. Now that I know they used the small motors, I can search further for original equipment prop sizes, etc., and at least know what they were using at the time. I agree, the small block power output has risen remarkably from those engines being used back then.
I've been reading a lot of David Pascoe lately (the marine surveyor) and here are some excerpts from his articles that apply to my search for economical engine replacements:
"The ideal situation is where the boat only requires 80% or less of the engine's maximum power to push the boat at the anticipated cruising speed. To further understand this, let's take an example. Say we have a 454 cubic inch gas engine which is typically rated at 350 HP, but in this case the engine is in a larger boat and has been bumped up by an engine marinizer to 400 HP. Now we have a situation in which the engine is not only putting out more power, but is pushing a heavier load. Just as you human body is going to wear out faster if you spend your life doing hard labor, so are those engines. Not only are they under more strain, but the higher horsepower translates to generating a lot more heat and friction. Each additional increase in horsepower over what the basic engine block was designed to achieve, reduces engine life drastically."
By reading this, I would rather settle for a mid power 350 than one with say, 350 hp. I think it would last longer.
Here's more (thanks David!)
"Another consideration, which many people find difficult to understand, is the relationship of torque to horsepower. Horsepower alone is not the sole criteria of how powerful an engine is. Torque is the amount of kinetic energy the engine builds up as a result of the rotating components -- crankshaft, flywheel and pistons. Torque is measured in the number of foot/pounds of power that is required to stop a running engine at differing speeds (In brochures this is often stated as the "power curve"). Most engine manufacturers provide torque/horsepower curves to illustrate the power range. Diesels, being heavier engines, as well as having more power with each stroke of the pistons, develops more torque lower on the torque curve. Gas engines develop their maximum horsepower toward the top of the curve, meaning the greatest power develops at maximum engine speeds, where it is least useable.
Torque is not a constant, but varies over the power curve, as shown in the graphs for a diesel engine below. Notice how there is a steep rise in the curve, and then how it flattens out near the top of the RPM range. Gas engines have curves that are the opposite of diesels, rising gently along the bottom, and then the curve shoots up sharply.
For heavier boats, the best engine is the one that develops its maximum torque lowest on the curve, meaning that the engine is developing more power at lower speeds. Since lower speeds mean less strain, heat and friction, these factors will translate into longer engine life, just as you will probably live longer with a regime of moderate exercise over a life of hard labor."
And here's more (thanks David!)
"There is a point in boat size and weight at which gas engines can no longer push the boat efficiently. This is usually around 35-38 feet and 16,000 lbs., depending on hull shape and the amount of hull and wind resistance. Boats with flatter bottoms require less power, as do low profile boats such as express cruisers as compared to a flybridge fisherman with a tower. For anyone contemplating a purchase in this size range, the ideal choice becomes rather clear. Remember what I said about operating engines on the edge of their power range.
Where Torque is Most Needed The torque/horsepower curve is most critical for those boats that operate at speeds only slightly above planing speed, e.g. the ones that are operating at the top end of the torque curve. But wait! Notice that the diesel engine torque curve begins to flatten near the top. That means that for slower boats, at the very point you need the most power, is the point where it begins to fall off. This is precisely the reason that you do not want to buy a boat that is underpowered: you will always be wanting to operate it at the worst possible speed.
The Dilemma Most questions of choice arise for boats in the 28 to 34 foot range where either type of engine is available with adequate horsepower. Gas engines have the advantage that they are cheap to buy and cheap to repair. Diesels are just the opposite; for the price of one Caterpillar 3208 of comparable power, you could buy three gas engines. For the price of a smaller, in-line 6 cylinder diesel, you could buy two gas engines. Thus, cost-wise, unless you really need diesel power, they are not very practical. The advantage of the diesel comes only at the point where the extra torque is needed because a gas engine would simply be under too much strain to have an adequate service life."
Having posted this info, I ask for more comments that may help keep me out of trouble, and or save me some money. I plan to use the boat just like I have for years, for day cruising. I normally find it hard to spend a lot of time on board, and when I do we normally don't travel more than 100 miles at a time.
Comments are welcome.
thanks again,
Dave
1964 38 Commander with original Lincoln motors
These SBCs have more torque and HP and the price is nice!
January 29 2006, 2:28 AM
IMHO. Both Crusader and Mercury have 6+ liter packages that are based on the 4" bore 3.75" stroke small block. These units pack over 320 to 375 horsepower and around 320 to 420 ft/lbs of torque from 1500 to 5000 rpm. They price in around $10,000.00 bobtail with EFI. Hard to beat- Less weight, more power, better fuel economy!
He fellas, some comments from the "been there/done that" peanut gallery
January 29 2006, 6:04 AM
I see several real advantages with the smaller motor. The 6.0 in particular, is the same external dimension as all small block motors, it gives plenty of power for the original 1-3/8" shaft on the early boats like Dave has, and it is so much lighter that it will literally compensate for the assumed power advantage of the bigger motor. In addition, if anyone does go with the bigger motor (as I have seen a few people at our Yacht Club do with older Chris Crafts over the years), they will have a tendency to want to use that extra power and on two occasions, we've seen props seperate from the shafts. I have also seen over-powered motors want to walk into the forward cabin too.
Chris Craft provided a larger shaft (moving up to 1-1/2") for their standard 300-hp motor, after experiencing an unacceptable amount of shaft breakages with the standard motor. Installing bigger power with the small shaft is a set-up for potential problems. If you're stranded out in the middle of Lake Michigan, or in front of an oncoming commercial freighter, it could be more than a problem.
In my experience the shaft normally breaks on the aft side of the cutlass bearing. Some times they'll just go "pfffft" and they're gone. They have been known to vibrate wildly and sling a blade into the bottom of the boat. On some occasions loss of a prop can grenade the motor due to immediate wide open throttle over-revving before the captain can figure out what happened. At full throttle with one engine still pushing with all it's might, this can sling the boat around, and it can be downright dangerous if you plow into a wave wrong or perhaps into another boat.
With the 1-3/8" shafts we're better off staying with similar power ratings to the original spec motor.
In looking over the material provided by Wes (thanks by the way for the links, Wes, this is good information and very convenient for surfing!) I am looking favorably on the 6.0 small block for several reasons.
First of all it's a small exterior dimension, and it would give more room in the engine bay than any of us who presently own the big blocks are accustomed to. Secondly it's lighter in weight, probably somewhere in the neighborhood of 500 to 800 pounds less than comparable big blocks of essentially similar power. The bigger motors are going to carry around that added weight where-ever they go as a handicap. It would be like having two or three BIG guys on the aft deck of your boat, whereever you go, in ADDITION to what ever load you happen to be carrying at the time. It takes fuel to push weight, and it would be like having several people on board all the time. Weight = horsepower any day of the week for boats and cars, so the 6.0 really looks like "the choice" for a 38' Commander, or a 35 or a 31 too. They look like fine engines, and I do prefer the Crusader just out of brand loyalty if nothing else, or perhaps I just like blue paint.
Dave, if you want to go out and break speed records and get the bigger motors, I suggest you change out your underwater gear to accept the larger shafts as a safety precaution. Big 3 or 4-blade props are expensive, and they can be dangerous if they have a mind of their own and want to rotate through the bottom of the boat!
In looking over this information, for the 38 Commander, doing what Dave has been considering sure appears to have a lot of positive factors. Since I may be faced with this same issue in the future, I'm very interested in the info that has been presented here.
Captains,
Lets not forget the new marine engines of today are all CRANKSHAFT rated horsepower and torque . The Chris Craft engines were all PROPSHAFT rated horsepower and torque . Most dyno operators will factor in a 10% loss thru the drive train . That new 6 liter GM marine version has peak torque above 4000 rpm which seems awful high for a big heavy cruiser . It sounds like uncharted waters .
Tim Toth , Sandusky , Oh
Crusader power ratings appear to be measured "at the propeller"
January 29 2006, 6:16 PM
Tim,
I just looked at the Crusader spec sheet, and they have a note that the power rating is "at the propeller" per NMMA procedures.
Maybe I'm looking at this wrong, if so please correct me. Wouldn't an engine rated at 375-hp at the prop, have to produce 415-hp at the crankshaft, in order to lose 10% power through the running gear and still end up with 375 at the prop?
Captains ,
Forgot to mention the web site www.marinepowerusa.com .It shows the different ratings ( crankshaft or propshaft )on there various models for torque and horsepower. I always considered peak torque was the optimum cruising speed . Forgot that Crusader only lists propshaft ratings .
Tim Toth / Sandusky , Oh
I'm with you Tim, about peak torque being the optimum, but on the 427 for instance, that's 2900 RPM, and there's plenty of torque available to throttle down to 2600 or 2700 and still be on a plane in my 38 Express. 2900 probably would yeild good fuel efficiency.
Hey, as long as we're talking torque, how about this one! This baby obviously had enough power out of the hole to get all those skiiers out of the water. Pretty cool photo, eh?
With a given prop and load, a boat will plane at a given RPM and speed (or not) regardless of the "torque" available. Additional torque at amy RPM will accelerate the shaft and increase RPM and speed. As the props are fixed pitch, ghe boat knows nothing about torque, it responds only to shaft RPM. True, it takes a certain amount of torque to drive the shaft at any RPM, and this depends on the hull, weight, and configuration. If you have more torque than is needed to drive the shaft at that RPM, the shaft speeds up.
It is rated at 300 hp and 355 ft lbs of torque and it reaches its max torque at 3600 rpm which is close to what you would cruise at for a big boat. It would be my choice and you can get them in carbed versions instead of the EFI. They are also making what they call power pacs which come without alternators etc.. but is a complete engine as far as intake manifold carb etc.. So there are many options out there and I agree with a few others the weight savings are something to look at. The current 350 w/trans is approx 900 lbs now a 1975 Chris Craft 350Q w direct drive is 964 lbs according to the sheet I got from the Mariners Museum so the new ones are lighter. But my Q motor only developed 235 hp at 4400 rpm and 330 ft lbs of torque at anywhere from 2900 to 3400 rpm the top of the curve is pretty flat. A Chris Craft 454 in 1975 weighed 1187 lbs w/direct drive trans and developed 330 hp so food for thought. Not sure what the difference would be when you go to 2.5/1 trans but it adds 7" to the length of the motor so I would guess it has to weigh more than direct drive.
One last note my 35 Aft Cabin weighs about 17300 dry and the 2 235 hp small blocks will push it pretty good ask Tim Toth he has been on it more than once for a test drive after whatever work we did that day. Usually after carb or ignition work I might add. We are having no more of that this year as the carbs are rebuilt and there are 2 Pertronix electronic ignition kits sitting here on my desk just waiting for their chance. My 2 cents is that I would look at the straight 350's or go with big blocks again the 6.0 is based on the corvette motor so it is a high revver for hp and torque, and you are talking that you dont cruise at speed so that to me would not be the best choice. It seems more like a small inboard motor like a ski boat or small cruiser w/ a single.
I said at the beginning of this thread, that I'm a big block fan, but I respect the daylights out of the SBC too.
I would opt for carbs if given the choice and a nice discount, because they're able to be pulled and worked on, as you know. If the EFI goes out, good luck.
The 6.0 Vortech is using HEI, injection, and high performance heads. In order for performance heads to work, they have to show-off by pumping lots of air, and that's the reason for the higher rpm rating. When Ford put together the 427 marine motor, they used generic heads from the 352 and 390 series of automobile, and that was a good thing for three reasons. Cost was low, the basic head was a good one, and the smaller valves helped build torque.
A big valve boat motor will have to spin fast to produce the power, and as you said, it would be great in an inboard speedboat. I'm with you, if I went with a SBC conversion, I'd opt for the carbed 350.
I'm just an ol' southern shade-tree wrench turner so plese excuse my confusion but-
Mark I have to disagree with your conclusion that- "the 6.0 is based on the corvette motor so it is a high revver for hp and torque..." I have included below for your review- the history of the SBC.
All of the marine 6+ liter SBCs I have found are based on the 4" bore small block (the 350)- not on the destroked 400 block (4.125 bore), with the change in CID aquired by increasing the crank stroke. The greater stroke makes these engines are torque monsters but this severly limits the RPMs (unlike the destroked 400 which can windup like a top!). The GM package hits around 380ft/lb of torque at 3600RPM with a little to spare. The big plus is the increased torque across the intire RPM range. These motors behave and have torque curves very much like big blocks but with the weight savings you have pointed out.
More torque (at any given RPM) with the same weight savings- I don't understand your argument? I do agree on carbs over EFI.
HISTORY OF THE SMALL BLOCK CHEVY
Since 1955 the small block V8 has won more races than any other.
Since its introduction in 1955, the GM small-block has powered more winning race cars and won more championships than any other engine in American motorsports. The small-block V-8 made its debut in the 1955 Chevrolet Bel Air by pacing the Indianapolis 500 and scored its first NASCAR win the same year.
The small-block was introduced in 1955 with 265ci. Unless you are restoring a car and want to be exact in every detail, the early 265 block is not one to use since it has no oil filter. During 1956 this was rectified and the engine continued in production until 1957.
In 1957, the engine size was stepped up to 283ci. This engine, with its 3.875in bore and 3.000in stroke, continued production until 1967. Up to about 1958 the small block Chevrolet used a rope type rear main seal, but from this point to the 1986 model the now familiar split neoprene seal was used.
In the 1962 model year the Corvette came out with 327ci. This was the first of the 4.000in bore motors, and set the stage for what was to become the most common bore size among small blocks. Equally note worthy is the fact that the stroke was increased to 3.250in. This necessitated larger counterweights and as a result, some substantial internal modifications had to be done to the 283 design to accommodate a crank shaft with larger counterweights.
In the 1968 model year when the 350 was introduced, blocks moved into the big journal crankshaft era and the 327 was produced both in small and big journal size. This means if you have a 327 big journal crank, you can make a 327 engine out of a 350. Later 327s from 19681969, when the engine was dropped, had bigger main bearing journals than earlier engines.
In 1968, the 307ci engine was introduced as a kind of economy engine. It had the 3.875in bore of the 283 and used a cast crank with the 3.250in stroke of the 327 and was produced up to 1973.
From 1967 to 1969, the 302 was produced, although it was probably developed just so Chevrolet had an engine size eligible for TansAm racing. In 1967, it was produced with the small journal crank and in 19681969, with the big journal crank.
The year 1967 also saw the introduction of the 350ci engine. This now classic configuration utilized a 4.000in bore with a 3.480in stroke, and has probably become the most common engine size. Along with the introduction of the 350 came the standardization on the big main journals.
The next major milestone in terms of performance was the introduction in 1970 of the 400ci block. This deviated from the standard format in many respects. First, it used a nominal 4.125in bore, as opposed to the 4.000in bore that had become the norm. To achieve the 4.125in bore, some internal casting core changes were necessary. The most obvious external change was the use of three freeze plugs in the side of the block. To accommodate this larger bore size, the bores were siamesed; there was no water between the cylinder bores because the barrels joined in the water jacket. In contrast, all other blocks have water completely surrounding each cylinder bore.
Along with this change in the bore size, the 400 motor was equipped with a 3.750in stroke cast crankshaft. To get this bore stroke combination within the confines of the standard 9.025in crankshaft center to block deck height it was necessary to shorten rod length if the stock piston ring package was to be retained. The standard 5.70in rod was then shortened to 5.56in.
In 1975, the 262ci engine was introduced with a 3.671in bore and a 3.100in stroke. It was intended as a low output economy engine but obviously did not prove popular as it was produced for only one year.
In 1976, the 305ci engine was introduced, which must be the most plentiful engine in existence, next to the 350. Built largely for emission and mileage reasons, this engine sports a 3.763in bore with the crankshaft stroke of the 350 at 3.480in. As of 1992, the 305 is still being produced and looks as if it will continue in production for some time.
In late 1979, a 267ci engine was introduced. This had a 3.500in bore along with the 3.480in stroke of the 350. Like the earlier 262, it was intended as an economy engine, both in terms of cost and fuel consumption. Again like the 262, it did not prove popular and was produced only through model year 1982.
As of 1983, only two displacements of small block were produced the 305 and 350. In 1986, a block design change was made concentrating on the rear main oil seal. Instead of having a split oil seal, the rear main bearing now used a full 360deg. one piece seal. Using this type of block usually requires using the relevant crank and flywheel, as a crankshaft design change was also made. If you have an early crank, Chevrolet has a special seal adaptor kit to convert 1986 and the late block to accept pre 1986 cranks.
A hydraulic roller version of this new block was also introduced at about the same time. The roller follower assembly is not interchangeable with later blocks. Unlike aftermarket rollers that are prevented from rotating by linking them in pairs, the General Motors roller setup has special slotted plates that locate lifters and keep the rollers aligned with the cam lobe.
Taken from How to Build & Modify Chevrolet Small-Block V-8 Pistons, Rods & Crankshafts, Motorbooks International, 1992
Wes here is my reason, it is not true that you are getting more torque at any given rpm look at the torque curves the 5.7 is much flatter than the 6.0 so thats why in his instance I am saying I would use the 5.7 for the fact that it actually does develop more torque at the lower rpm ranges. Here is the data you can see that at 2000 rpm the 5.7 is developing more torque. That was my thought process for his specific circumstance of low rpm cruising. I have a friend who has a Baja with the new 496 HO mags sweet motors but designed to be run at 5000 + rpm for power they have been worked on more than once under warranty and I feel it is because of how the motors are used high rpm's for sustained running on the lake. Cruise for him is 4500 rpm's at about 50 mph this is his second new Baja the 32 had multiple instances of blown motors and his 38 has been in the shop more than once. No he didnt do anything wrong that I know of but he has lost lots of time on the water.
Ok...ok I did say I'm an ol' (uneducated) southern shade-tree wench er I mean wrench turner.
You'er right on with the torque figures and after looking harder at the info the GM package it is not the motor it should be! The 6 liter GM uses a 3.62 stroke but with the Alum heads she gives up lots of bottom end torque. I base my argument for a SBC 6+ on a stroke of 3.75 or better- more like the Merc and the Cursader packages. I'd go with the Cursader in a heartbeat if I could afford them! But- bein' a poor ol' ... I'll jus have to settle for buildin' my own (which I am!).
My argument still remains the same- for any given engine if everything remains the same (appels to apples) and you increase the stroke- you increase the torque and reduce the maximum RPM.
Here is the stats on a GM small block with a 4" bore and a 3.80" stroke to help make my point. The Merc and Crusader both have the longer throw 3.75 crank.
SMALL BLOCK POWER
TO GO
Specially tuned for torque, the all new HT 383 delivers great
power in a small block package. With its 3.80" stroke and Vortec cylinder heads the HT 383 makes awesome torque, down low where you need it. Peak torque is 435 ft.lbs. at 4000 rpm, but the HT 383 makes over 400 ft.lbs. from 2500 to 4000 rpm. Developed with a roller cam, special heavy duty forged powdered metal connecting rods, “4340” forged crankshaft and hypereutectic pistons the HT 383 is designed to be worked. 340 horsepower at 4500 rpm doesn’t hurt either. The HT 383 is an ideal replacement for any 1978 and
older carbureted engine.
HT 383 Technical Information
Horsepower ..................... 340 @ 4500 RPM
Torque .......................... 435 @ 4000 RPM
Max. Recommended RPM ..... 5000 RPM
Compression Ratio ............. 9.1:1
Partial Engine ................... 12498332
Block ............................ Four bolt main, cast iron
Crankshaft ...................... 12489436 Steel “4340”
Connecting Rods ............... 12497624 rods
Pistons .......................... 12489437 High silicon aluminum
Piston Rings .................... 12522848
Camshaft ........................ 14097395
Cylinder Heads ................. 12558060 Vortec
Intake Valves ................... 10241743 1.940"
Exhaust Valves .................. 12550909 1.50"
Valve Springs ................... 10212881
Rocker Arms .................... 1.5 stam steel
Intake Manifold ................. 12496820 Aluminum dual plane
w/dual carburetor pad and EGR
Tortional Damper ............... 12498008
Flex Plate ....................... 14088765
Spark Plugs ..................... R 44LTS or Rapidfire #3
Fuel ............................. 87 Octane
Ignition Timing .................. 32° total @ 4000 RPM with vacuum
advance disconnected
Technical Note: GM recommends a Rochester Quadrajet or Holley 750
CFM carburetor for the 383 applications.
This engine is available as P/N 12497317 it is called the HT 383.
The 383 stroker is legendary in racing (and boating) circles. I know a guy who ran one against Keith Brayer in his hemi powered Racing Runabout, and lost! Brayer has the advantage of V-drive, and of course his dad, Curt, is a two time APBA record holder and was "high point man" 7 years straight, so they know the "black magic" of making one run.
that crank you're talking about is awful close to the 427. I'm tossing this in for comparison.
Except one problem neither the merc or the crusader comes in RH rotation only LH rotation, so what do you add in the price of Bi Direct V drives and re-engineer the whole engine compartment? I still say go with the 5.7. Crusader will sell you both LH and RH in that model either as bobtails for about 15k or with reduction transmission for less than 20k as compared to 6.0 with Bi Direct V drives will set you back 25k plus the whole mess of re doing the commander to fit them in. I'm trying to base this on what Dave Mehl posted originally not just the apples to whatever comparison of the 2 different motors. I am thinking how I would do it based on his post given overall costs and ease of installation. I would not want to have to re-engineer the boat to make a motor work and I am not a big fan of V Drives. I understand their application for smaller express cruisers and the added savings of room they provide but room isnt an issue and I would take straight inboards over v drives any day (just my opinion). Now I know you will find some one making the 6.0 in a RH roatation but for how much? And is it worth the additional cost? He is talking about resale value down the road and ease of someone else posssibly replacing with big blocks. I'm not saying the 6.0 isnt a great motor I just feel the 5.7 is a better choice in this instance.
Yep it's alot more than just changing an engine or two.
January 30 2006, 10:39 PM
Mark,
You're right about the 383s only being offered in a standard rotation (nobody makes reverse rotation roller cam blanks appears to be one of the reasons) and I'm glad you mentioned this. I have been looking at this from the point of view that it would be less costly to try and match the BB torque/RPM curve and keep the same props, shafts, reduction ratio, and have the same "feel" of the vessel but with a weight savings. Dave had mentioned that he was giong to replace his transmissions and I in my total stupidity of marine transmissions assumed a couple of $1700 72s with one of the pump housings rotated would take care of the standard rotation problem. Those and a couple of these "puppies" http://www.musclecarengines.com/marine_engines.htm
would come in at under 20k and well... DANG I'm drooling! Having to redo the vessel for V-drives however sounds like way way to much work and counter productive! Maybe a new thread on marine transmissions is in order? I sure could use the info and I think that anyone that cares to read all of this thread is well aware by this time that the SBC in whatever form is a fine marine engine and that a repower is much more than just pullin' and puttin'. Anybody for a marine transmission thread? I sure could use the info!
Looking over the auto parts catalogs, there are hundreds of cams I can select for LH operation, and I have found some that I think will work very well in a marine torque application. Everyone I call says they only have automotive rotation. Is there a place that also provides a selection of cams in the RH rotation?
I saw your note and decided to call Comp Cams, 1-800-999-0853 just to check it out. Their tech department said they had 15 blanks sitting on the shelf right now, and they would grind them to any profile you wanted. Therefore, if you find a cam that does what you want by reading their specs, such as a towing package limited to 5000 rpm or less, they can duplicate it in a RH rotation too.
Here's a list of cams they offer for the small and big chebby motors. They are available in LH or RH, and for our old motors they can get them in flat tappet or hydraulic, but only in the "stock profile". Stock to them means, the same marine profile used in Mercruiser, Crusader, whatever, and not in something aggressive for racing.
......and they said it again about the 327. However, both the 283 and the 327 were about as tough a motor as you'll find, real work-horses. One of the reasons they enjoyed working was they weren't asked to work too hard. The torque was there at a reasonable rpm and the power was adequate (most of the time).
I was taught to not try to plow a field with a race horse, but to use a work-horse for much better all around results.
Check out these specifications against the new motors. It will help evaluate what should work well in the "cruiser marine" application rather than the runabout application.
Those of us that had 57 chevys remember these mighty mouse motors real well!
283-Inch Small-Block Chevy
The Facts
Under the direction of Ed Cole, the Chevy 265 cid V8 was rushed into production and was introduced in 1955 along with Pontiac’s 287 cid entry into the market. The new engine had some initial teething problems but these were quickly resolved and the Chevy small block evolved into the most successful V8 engine of all time with over 16.5 million being produced in ten different displacements over the next forty years. It is still with us today as the 5.7 liter (350 cid) V8. It saved the Corvette from extinction and restored Chevy to its former dominance over Ford. Despite numerous design improvements over the years the engine’s basic geometry and key dimensions have been maintained unchanged. This continuity has contributed to the interchangeability of parts and tremendous popularity of the small block amongst performance and other enthusiasts. The availability of original and aftermarket parts for the small block Chevy V8 is not equaled by any other engine.
The 265 in the 1955 Corvette was rated at 195 HP, a substantial improvement over the six cylinder. For 1956 maximum HP for the 265 was raised to 225 HP. In 1957 the 265 was bored out to 3.875" resulting in the venerable 283 cid engine. Horsepower available for the Corvette was raised to 283 HP with fuel injection. In 1962 the 283 was bored and stroked to produce the famous 327 cid engine. The 327 was available in the "fuely" Corvette with up to 360 HP. A stroked version of the 327 was introduced in 1967 giving 350 cid.
The 283/283hp fuel-injected engine was among the first of the American engines to dispense with carburetion and make 1 hp/ci. Under legendary Corvette engineer Zora Arkus-Duntov's tutelage and encouragement, a slew of factory and aftermarket parts were developed for the 283. With a large variety of parts available, it became easier and cheaper to coax horsepower out of a Chevy small-block than the competition's engines. More enthusiasts gravitated toward the "easy to work on" Chevys, which encouraged the development of even more parts--and so the Chevrolution became self-feeding.
Even after the 327’s debut, the 283 made such a good base engine that it soldiered on through 1967. With its short 3-inch stroke, a 283 can rev as if there’s no tomorrow, but the small bore restricts adding really large valves and, hence, ultimate breathing potential. Except for the Vette 283/315hp option, 283s never came with anything larger than 1.72-/ 1.50-inch valves. You can install only 1.94/1.60 valves without hitting the cylinder walls. The 1.9:1 rod/stroke ratio is on the high side for an acceleration engine but great for an endurance or oval-track engine that runs at a high, constant speed. However, there’s no getting around the fact that a 283 just gives up too many cubic inches (and too much torque). Unless you’re into nostalgia, restoration, or class racing, there is no real reason to build a 283 today.
Highlights and Evolution
- 1957: The first 283 block is similar to the 265 block, retaining the driver-side breather tube and lack of side motor mount lugs. However, the rear cam-bearing area is redesigned, eliminating the previous requirement for a grooved rear cam bearing. The '57 blocks are thin-wall castings and shouldn't be overbored more than 0.030 inch.
- 1958: Side motor mount lugs are added to the block adjacent to the front freeze-plug hole. The new-design thick-wall block can be bored 0.125 inch over for street- or mild-competition use (0.060 inch for professional-race use).
- 1959: The block is redesigned to eliminate the pesky rope-style rear main seal in favor of the two-piece neoprene-seal design that was used on all small-blocks through 1986.
- Early '60s: Chevy changes over from cast-iron to aluminum manual-trans bellhousings and torque-converter housings, in the process relocating the starter mount from the bellhousing to the rear passenger side of the engine block. Earlier blocks usually are not tapped for starter mounting.
- Both forged and cast 283 cranks exist, the latter first appearing in late 1964. The 283s originally equipped with a cast crank have a full harmonic balancer; 283s produced with a forged crank only have a harmonic-balancer hub.
- 1962 and up: Many 283 blocks are produced using the 327 tooling. This means they have extra-thick cylinder walls. You can usually bore them up to 0.155 inch over (4.030-inch bore, 306 ci with a 3-inch stroke). The cylinder walls on these desirable 283 blocks are dished to clear the 327 crank (plain 283 cylinder walls are perfectly round on the bottom). The best of the best is the Chevy II 283/327 casting no. 3790721; besides extra-thick walls, the block has a higher nickel content than standard blocks.
I am at a loss of words for any follow up to this fascinating discussion thread. Although I have 2, 350 pseudo F Chris Craft Engines in my 31, I’m partial to big blocks. Attached are Pictures of my 390 FE, in my runabout, which originally was a 352. Guys keep up the thread I enjoy the reading.
Tom and Barbara FXA-31-3016H
Nylakeshome@yahoo.com
Tom, you're a man after my own heart....having a 390 in a runabout
February 11 2006, 9:04 AM
That's a great looking installation. Bet it sounds good on the water too. I went the SBC route with my runabout, and I regret it now simply because I'd rather have a big block Ford. The SBC goes fast enough, but at almost the same weight, it would be my preference to have the big dog.
So that 352 originally put out 250-hp, and you changed over the crank to get 390 cubes? Interesting exhaust manifolds, Interceptor, eh? What's the gauge on the rear section of the motor, fuel pressure, oil pressure, water temp?? Just curious.
I was working on my speedboat this afternoon, installing a new water pump, hooking up a large fuel filter, looking over the carb, etc. Then I looked over at the two spare 427 motors sitting in the corner of the garage, too bad I got those long after the motor swap on my 1956 17' CC Sportsman Utility, because otherwise it would have a 427 sitting there now.
That transmission on yours is probably 1:1 direct drive. Of course you know there's no problem at all getting 300 hp from a 390, and it would run all day long at that power rating.
Paul, the gauge mount on the rear is an electric hour meter. I wanted an accurate measure of hours as compared to the mechanical hour meter integral to the tachometer.
The transmission is a 1:1 Borg Warner Velvet drive, there is no better. I wish Chris Craft had used Velvet drives! It is an Interceptor Dearborn conversion, with aluminum manifolds. I have many spare parts, hunting around the local marinas. Trojan cruisers used FE Interceptors in many of their boats in the 60’s. I did replace the insides of dual point Mallory OEM distributor with an electronic unit. Runs great without breaking up at 4700 rpm and 55 mph.
You are correct new crank pistons and cam. The cam was a bear to find, it’s a reverse rotation. I found one about 11 years ago. I doubt, you could find a new one today. Nothing like those solids lifters at high rpm when she’s cranking.
Tom and Barbara FXA-31-3016H
Nylakeshome@yahoo.com
