So the goal is to run the the engine at max torque, not horse power? Been around boating and boat racing a little bit, and have not seen this before. But they all had propellers.
Horsepower is nothing more than an equation of torque over a time component, in this case RPM. So Horsepower = (Torque x RPM) / 5252. The key is to build max torque in the RPM where its needed to achieve max horsepower input into the jet. Props can use low end torque to launch skiers, or launch a boat down the Firebird Raceway. However, low end torque means nothing to a jet as it can't use it. You can take a jetboat, tie the transom to a great big tree on the shore, and run it to WOT...and as long as it doesn't cavitate, it will pump water at full power while standing still.
Horsepower requirement of a jet is a non-linear graph, increasing HP demand as the RPM exponent increases as by this equation: Horsepower required = (RPM/1000) *3 x (impeller KW rating) x 1.34. My jet is currently configured as 4.05KW, the 1.34 is a KW to Horsepower conversion constant. So you can see that say at 1000 rpm, my jet requires 5.4hp/28.5ft lbs, at 2000 rpm = 43hp/114ft lbs, at 3000 rpm = 146hp/256ft lbs, at 4000 rpm = 347hp/456ft lbs, at 5000 rpm = 678hp/712ft lbs, at 6000 rpm = 1172hp/1026ft lbs. Since my motor maxes at 4500, it requires 494hp/577ft lb, so increase more RPM input into the jet, more torque is needed in the 4500-5000 rpm, hence the reason why I'd like to stay with a 110* LSA and increase the duration to move the peak TQ up into that area, vs the small cam that I have now.
