Prop pitch influence on staying on plane

[Eric.G]

Hello all,

I have read several post that make the statement that a lower pitched prop will help you stay on plane at a lower speed.
Im having trouble seeing the rationale behind that statment. It would seem that at what speed a boat comes off of plane whould be influenced by hull design and the weight of the boat.
Unless were talking about a 4 cyl or a smaller 6 cyl that might not have enough torque to keep the prop turning at, say, 2200 - 2500 RPM, Im not getting it.
Can someone help me see the light?

Thanks
Eric

 

[BaileysBoat]

Re: Prop pitch influence on staying on plane

Hull design is the primary determination of planing speed, although some stern heavy boats can benefit from a stern lifting prop.
The correct prop allows the engine to be in the rpm power band to maintain planing speed just off of the step without lugging. If the engine is lugging it will want to fall off the step and require constant throttle adjustment. Running at 2200/2500 is too low for most boats to plane.

 

[steelespike]

Re: Prop pitch influence on staying on plane

what he said^ A lower pitch will allow the motor to be able to hold plane/speed better against
against waves,wind and load.

 

[SparkieBoat]

Re: Prop pitch influence on staying on plane

trim tabs will help better

 

[emilsr]

Re: Prop pitch influence on staying on plane

A lower pitched prop MAY help the engine stay further up in the power band. There also MAY be less prop slippage, providing more forward thrust.

I say MAY, because there are many other factors involved here. That's a very general statement and won't be true 100% of the time.

 

[Texasmark]

Re: Prop pitch influence on staying on plane

I have 3 Ballistic SS props for my current boat pitched: 17, 21, and 24". So, I have everything a constant other than pitch selection.

The 17 will snap your neck on a hole shot but my engine is almost at redline as soon as the boat planes out. I can hold the boat at a 45 (ish) degree angle if I want right at the point where the boat would normally drop the bow and plane out. Ultimate control of the attitude of the boat without any throttle change (jockeying) once I am where I want to be.....45 angle (grin).

The 21 is obviously a compromise.

The 24 is the one I use because I run a light fast boat and I don't have to worry about heavy load stress. I ported the prop to improve the hole shot which it did in allowing the engine to develop it's rpm's earlier in the "take off" cycle (unloads it under the hole shot stress). Obviously, right at planeout speeds, this prop requires constant throttle manipulation to correct for changes in environment...wind, waves, boat settling and all.

So, you can't get a plainer answer than that. "Pitch" does matter!!!!!! This isn't the first boat that I proved it on.

HTH,

Mark

 

[Eric.G]

Re: Prop pitch influence on staying on plane

Thanks for all the replies.

So, with the exception of stern lifting type props, it seems the real issue is the props relationship to the engines power band at the point your about to fall off plane. Nothing magical the prop itself is doing. Thats pretty much what I was looking for.

Thanks again

Eric