I have two props with the following information;
Chris Craft equi quad 2448RH (10-83) and 2449 LH (10-83).
I think these are original props on my "84" 410 commander. I also think they are made by Federal/Michigan wheel. Can anyone tell me the pitch? I'm pretty sure they are 22" diameter. Any feedback on prop scanning?
Thanks,
Rick

2448 Quad 22x22 1-1/2" shaft, RH
2449 Quad 22x22 1-1/2" shaft, LH

Hope this helps! Remember, a 4 blade prop is probably going to be two inches less pitch than an "equivalent" 3 blade prop.

Regards,

Paul

Thanks Paul.

Paul,
You said that if I go to a three blade prop from my existing four blade 22X22 props I should go to a 22X24. Is that correct? There is a set available that are 22X24 3 blade and I wonder if they would work and what I would give up by going to a 3 blade.
Thanks,

Hi Rick,

That's my opinion, but it is not an engineering opinion, it's from my own experience and from what I've read.

It's my understanding 4 blade props simply create more friction at top speed and can not match a 3 blade, and that is why you see virtually all race boats with 3 or 2 blade props. Where the 4 blade seems to work better, is in the lower end of the spectrum where you want to manuver a boat in the harbor and at mid range cruising speed. They have a better bite for some of the ski boats too, and they are supposed to be a little less vibration prone but I really didn't notice all that much difference over well balanced 3 blade props.

They're not a silver bullet. Chris Craft did exhaustive testing with various props for each boat and their experience will always outweigh the boating enthusiast who is looking for something in the way of speed or fuel efficiency, again in my opinion. Best to stay with the specified prop most of the time, but you will find the people who engineer and make 4 blade props will say there are advantages, and Chris Craft installed these on boats like yours for a reason.


Here is one of the beautiful 4-blade props I put on TRADITION, original props were 23x25 for the 38 Express, and I installed 23x24 4-blades. As a result the boat will still fly, but I am not getting the full benefit of the nearly $1000 cost for each of these props because I'm over propped at the time, and I can not reach full RPM with the engines and therefore have concluded these should have really been 23x23. Next time the boat is out, I will reinstall the newly balanced 23x25 3-blades and send these off to be repitched to 23x23.

The only real way to tell for sure is to do what CC did with each of their new boats, and that is to try it. If you have a 22x22 4 blade on the boat, and want to go to a 3, I would think a 22x24 would make an interesting swap, might even get a tiny bit of additional speed, but might lose something in the middle range. As the Brayer boys have advised on numerous times, "it's not an exact science", and their brand of "black magic" along with a good understanding of engineering principles and great driving skills is what won all those APBA races for Curt.

Anyone out there with similar or different experience swapping props from 3 to 4 blade, or vice versa, please chime in.

Regards,

Paul