Does anyone have the graph for HP/ fuel usage
for a 1988-89 454 mag 365hp?

No one has this?
Or does anyone know the fuel burn rate at certain RPMs?

rob

fuel burn rate would vary depending on the boat it was in. a heavier boat will require more throttle to maintain the same rpms vs. a lighter boat. same reason you get worse gas mileage towing your boat vs. driving your truck unloaded.

Are you sure that's right?

If an engine is turning 3000rpm it needs so much fuel to turn. Why would it need more fuel to turn the same RPM.
I understand you need more rpm to run a greater speed in a heavier boat.
But shouldn't rpm be rpm under any load?
Isn't the fuel metered to a specific amount per cylinder per crank turn?

nope your truck runs the same rpm at 70 with a load or not but you get different mileage pulling a load vs. running empty

an engne under load will burn a lot more fuel than an engine running under a light load at the same rpm. So the fuel curve will vary from one application to another.

All you can say is that at WOT you will burn between 35-40 GPH per motor.

Thanks guys, that is the info I was looking for.
I'll be installing a fuel flow meter that has a 35gph max.

If WOT is 40gph, than I'll be under 35gph more than 95% of the time. Which means the damn thing should be pretty accurate. As opposed to cruising at 3200-3400rpm burning 40gph.

This is what I just got from Merc.
1600rpm 3.6gph
2500rpm 7.3gph
3500rpm 13.4gph
4500rpm 24.3gph

that is as high as they go.

Also depends on the size of prop you turn and the load it creates. I get better milage and mor RPM's with my 23 pitch but the GPS says the 25 pitch is faster at a lower RPM's and uses more gas. go figure Rag's

Just plan on spending lots of $$$ on gas this summer anyway