So, I have a 454 with 300cc aluminum oval ports, crane 731 HR Cam, Roller Rockers, IMCO Powerflow high flow marine manifolds, air gap intake, holley 800DP HP500 Carb in my 23.5' bravo 1 boat.
I am not spinning the Prop to the RPM I should be. I swapped between the two props I had, and the RPM is equivilant for the respective prop's pitch. So it's got to be the engine.
Only thing I didn't change is the fuel pump and I'm still using the small flame arrestor as others said the stock pump should be fine up to around 500HP and I doubt I'm too much over that.
I can't find anything else wrong with the engine, timing is about 37* all in around 3000-3200, engine sounds strong, runs strong, gets on plane fine. But won't spin as fast as it should. Would it sound terrible, pop, backfire,miss, etc if it was running out of fuel? or will it just run out of steam? Is it possible that it does just need a bigger pump?
Or, is the stock small flame arrestor not giving the air flow for a good enough vacuum signal?
Or, I have no idea what size jets or PV that are in the carb, it idles fine, and starts fine. But, could it need larger jets? Carb is stock mercruiser off of the 500 HP 502, so I assumed it'd mate my combo very well. (I realize what happens when we assume things though )
Could spark plug gap keep me that low on power?
Its got new plugs, wires, cap, rotor, coil. it is a stock coil.
I have not done a compression test or a leakdown test, I'd really doubt that'd be my problem judging by the vacuum reading, and also, how hard the damn thing is to turn over by hand. Its got compression.