Prop size help please!

[procleanguy]

Hello all, we got out new to us boat out today and the prop is to small of pitch I believe. It's a 1991 prowler by cooper yachts with a 3.0 lx 140hp. It has a 15x17 prop on it. Today with full tank and 2 people trim all the way down and it would easily go over 5000rpm. I didn't want to push past that and backed off. Hit 36mph on GPS at 5000 rpm. What prop should I move to? I see a few used stainless props local to me, 14x21 and 14 1/4x21. Would that get my rpm down or should I stay 15" and 19 or 21 pitch. It's so confusing and I don't want to buy multiple props. Thanks!

 

[jimmbo]

First thing is you need to know what the WOT Rpm Range for your engine is. 5000 is a bit high for that engine, so you will need more Pitch. I would talk real nice to a Local Dealer and see if he/she will let you try a few props, on the on the Condition that you will be buying One, and any that you damage(which includes any Paint Scratches). I would start with a 21 inch and see where that puts the Rpms. I/Os usually have a WOT Range 400 rpm wide. and every 1 inch change in Pitch changes the Rpm by 200. Most Boats ship with a Prop in the 19 - 23 inch range, regardless of which Engine is in the Boat. That is why different HP engines have different Gear Ratios.

 

[Bondo]

Hello all, we got out new to us boat out today and the prop is to small of pitch I believe. It's a 1991 prowler by cooper yachts with a 3.0 lx 140hp. It has a 15x17 prop on it. Today with full tank and 2 people trim all the way down and it would easily go over 5000rpm. I didn't want to push past that and backed off. Hit 36mph on GPS at 5000 rpm. What prop should I move to? I see a few used stainless props local to me, 14x21 and 14 1/4x21. Would that get my rpm down or should I stay 15" and 19 or 21 pitch. It's so confusing and I don't want to buy multiple props. Thanks!

Ayuh,..... Welcome Aboard,..... Sounds like you need a 19" pitch to get the rpms back down to 4800,.....