What's been overlooked here is that he is running 5000 RPM with the A impeller.
Some years back I built a mild 454 for my friend's jet boat that also turned an A impeller 5000 rpm, showing about 62 mph on a non gps speedo, but routinely beating 18 foot jets with headers, while his 20' open bow had through transom exhausts and covered engine. Made lots of guys mad.
The engine was installed into the boat with the 715 cfm (Yes, Holley made them) OEM carb, and did pretty well with it. One day he ran out and bought an 850 Holley without asking me first, and was surprised that the boat actually lost power until he and I did quite a bit of messing around with jetting, and in the end made no actual gains.
I have built some comp jet race engines that were turning smaller impellers into the 6200-6500 rpm range that did run single Dominators, and one of them out-powered the tunnel ram boats at Burley badly enough the other competitors were talking about protesting it. I assure you the engine was 16 cubic inches under the maximum allowable limit, with absolutely no porting in the heads or intake, they both still had APBA spec lettering in them. That particular boat didn't do well in rough water, or it may have shown similar results at other races. We are in the process of rebuilding that engine with new heads, and the ultimate plan is to dyno with both single Dominator and tunnel ram to determine the actual difference, but if the impeller limits an engine to a given RPM below it's actual maximum horsepower, larger CFM rating may not be doing much for it?
