Prop Pitch ?'s

[MBAKER]

All of the info i see about props talks about running it at WOT to see if you are in the power band or not. But my question is, if we rarely ever run at WOT, should i really be concerned with top speed. More often we are pulling a tube or skiers, and top speed is not a concern, even without the tube we rarely run at WOT beause the ride tends to get rougher. I know the prop we have will let the engine overrev, but i can deal with that to gain the holeshot, just wondering if I am giving up something else in between.

We have a 15P prop right now, and it will overrev a couple hundred rpm but its not a big deal. I was considereing going to a 13 4 blade just to try and get a really good holeshot and up out of the water faster with a skier/tuber, but maybe that would be overkill?

Is there a point where you go too far and underprop a motor and start to hurt the holeshot and midrange performance? Like the prop spins and gets rpms up, but maybe slips more or doesnt have enough forward push to accelerate the boat?

Any thoughts?

 

[jevery]

Re: Prop Pitch ?'s

Go as low as you want to improve holeshot, but throttle back to avoid over rev or risk throwing a rod through the block. Top speed will certainly suffer. Also a low pitch prop will produce a higher RPM at ANY given speed potientially decreasing engine life over the longrun. You need to find a reasonable balance. I wouldn't want my boat to hit max RPM at 40 MPH when it's capable of running 55 MPH, unless my primary concern was pulling three slalom skiers out of the water.

 

[Silvertip]

Re: Prop Pitch ?'s

Your WOT question gets asked a lot and the reality of it is that if the prop is incorrect, it doesn't matter what speed you run it. The prop is still incorrect. The correct prop is one that allows the engine to run at or near the manufacturers recommeded WOT rpm. That's the ONLY way to tell whether you have the right prop. Yes you can go too far either way. Too little pitch you over rev -- too much pitch you lug the engine. Neither is good for engine longevity.

 

[MBAKER]

Re: Prop Pitch ?'s

I understand that too little pitch will overrev and too much will lug the engine and the effects of both on engine longevity. I guess my thought was if we never run at WOT because usually the actual speed of the boat is too fast for the water conditions, then maybe there wold be a benefit to lowering the pitch and bringing the rpms up at cruise speed, to keep the engine closer to the power band as well as help with holeshot. Top speed doesnt really matter to me as we never run that fast anyway.

Ill admit im pretty new to all of this, jsut trying to learn. Just seems like I see a lot of stuff concentrated on top speed conditions, but maybe im missing something else that doesnt allow us to run that fast on rougher water.

 

[Silvertip]

Re: Prop Pitch ?'s

high revs due to lower pitch numbers means the engine burns more fuel than it has to. Too much pitch means the engine lugs which requires too much throttle to maintain speed which also burns more fuel than needed. So I repeat -- the correct prop is correct at all speeds. An incorrect prop is incorrect at any speed.