Originally posted by XcellR8:<br />
Originally posted by walleyehed:<br /> 2 different hulls reacting totally different to 1 blade design....no apples to apples here.<br />4400RPM is going to get the best of your engine, as in ruin it..5600-5700 would be a good target, but just changing props isn't always the answer.<br />Do we know we have a good, healthy engine?? How about fresh fuel?? Is the engine mounted on the transom clear down, or raised any??<br />Some people mount a prop more for looks than actually mounting the best option.<br />We may have a possible tach issue as well, because I believe a 21P should not be over-propped on a 90 mounted to a 15-1/2ft boat.
I'm not ruling out the possibility it could be the motor, just that most of people I talked to said that's an awful lot of prop for that motor. Fresh gas was the first thing I did as soon as I brought it home. I'm not sure how healthy the engine is because I only heard it run on the muffs before I bought it(too much debree in the river to take it out). The compression was 150-147.5-145 when I checked it. It seemed to run fine, idle is a little rough but it doesn't stall or anything. I'm not sure how old the plugs are but they didn't look too bad so I didn't change them (the dealers I talked to told me the gapless plugs don't foul and that they should last about five years).<br /><br />The first time out I thought it seemed to rev kind of low and labour when I was just in gear with barely any throttle applied (I launch at a shallow creek so you have to travel slowly for the first little while). I bought a brand new Teleflex tach, set it to 6 pulse and checked my rpms the next time out. That's when I noted the 4400 rpm @ WOT (I'm not sure how accurate boat tachs normally are but if they are like sleds they read a couple hundred rpm high). <br /><br />I borrowed a 19" pitch, 3-blade aluminum to try and it must weigh about a 1/4 as much as the Trophy Plus. The only problem is I can't get the brass bushing off the prop shaft to replace it with the one that goes with the aluminum one. Do you need a puller or something? Wouldn't all the extra weight of the SS really slow down how quickly the motor can bring up the rpms when you punch it (kind of like a big flywheel)?
