Hi Tom,
Your engineering background is coming through loud and clear! I tend to agree with most of your comments for the reasons stated.
I think the fuel consumption will vary between boat to boat, based on many factors, and the published info is a relative guide for the consumer.
When comparing data, especially data from say, 1964, with data from the 1970s, it's important to know the conditions surrounding the gathering of data.
Here's one for you! The Lincoln 430 has been unfairly painted as a gas hog by some, but look at the numbers in the actual on-the-water test from Hank Bowman. In addition, now I wonder if those numbers are, indeed, on the water test numbers from Hank or from Chris Craft. It's dangerous to take a number and run with it, unless you know how that number was arrived at.
http://www.network54.com/Forum/424840/message/1173461961
Using your example of 2800 rpm as a baseline, the 430 Lincolns got better fuel economy than later published data from CC for the 427.
Your point about being used for relative consumption is a good one.
regards, Paul