Originally Posted by BSB67
Originally Posted by fast68plymouth
Since there is a formula to determine how much power is required to turn the pump a given rpm, the goal is to make that amount of power, at wot, at that rpm.

It doesn’t really matter if that’s the engines peak power or not.

As long as the pump load and the engine output are equal at wot, at the desired rpm....... that’s as high as the engine will rev.



Right, but then you've built the wrong motor if the peak hp is at much higher rpm.


Dwayne is 100% correct, I am targeting the engines output to turn at or near 4800 at WOT, as that is the pump's input rpm that equals the max torque output that a typical 4.15" stroke RB block is capable of producing, in naturally aspirated form, and cam the engine for that rpm target. I don't care if the pump won't allow the engine to run at peak HP, as re-configuring the jet for a lower KW rating to achieve that peak, is not the ideal configuration for pushing an 8,000lb boat up through a class 5 rapid...for a 2000 lb Sprint boat on a race course, then go ahead and tune the jet for peak motor HP. But to tune the motor to match the max horsepower rating of this jet, then not many on this forum have such an engine and I would be best saving my money for Mercruiser QC4V or GE T-58 turbine.


Last edited by mgrant; 10/30/19 12:20 AM.