ProMax horsepower curve

[Jimxb02]

I have a 225 promax with bolt on mods --- Brocato SVS, Rapair ECU with no rev limiter, Jay Smith light flywheel, 150 lb heads, tunner and exhaust relieved, oil injection removed. The motor is stock internally --- block, ports, exhaust chest, cast pistons ( top pinned ) all stock.

I can spin the motor to 7900 RPM with a 26" chopper II ; but I don't want to run it that high.

The question is ;;; what does the horsepower curve look like, where is peak power and when does it roll off, 7200, 7500 ?????

Help, you guys with some dyno time or merc spec sheets.

Jim

 

[John Richied]

I don’t have a dyno sheet, but my 225 ProMax is set up the same as yours with the exception of I did not have the tuner and exhaust relieved.

With the SVS I think it moved the powerband down and wider so it would pull harder from 4200 to 7500 Rpm’s with a 24 or 26 pitched prop. However I think a dyno sheet would say 4800 to 7250 is where the best horsepower/torque curve is based on with a bigger pitched prop or loaded it ran best in this area.

Mine wouldn’t pull much past 7500 with 150 compression heads, but with the 26cc/180-lbs. drag heads it would pull to 7750 rpm’s.