Anyone tried, or heard of, a sharrow prop on a 228?

[Ekea]

As I understand, it the planing speed is a function of the hull shape not the motor. Sharrow props can plane at lower rpm due to less prop slip but the planing speed remains the same. As others have said a prop with more “grip” (eg. 4 blade) might reduce the amount that the boat falls off the plane but it won’t reduce the planing speed.

a prop can be designed to provide stern lift, and it can be significant. stern lift can reduce minimum planning speed

 

[SeanC]

I would disagree with the prop part of your statement. Props can have a significant impact on an outboard powered boat's attitude and planing speeds. I won't claim to know all the details, but many prop geometry details will impact this. Barrel length alone can have a significant impact.

Yes I understand that different props can produce different amounts of stern lift. You can also achieve as much stern lift as you want by trimming the motor under or using your tabs. So I’m not sure how stern lift by the propeller reduces the planing speed more than other methods. Just thinking out loud.

 

[family affair]

Yes I understand that different props can produce different amounts of stern lift. You can also achieve as much stern lift as you want by trimming the motor under or using your tabs. So I’m not sure how stern lift by the propeller reduces the planing speed more than other methods. Just thinking out loud.

Planing is a result of the reactive force on the hull producing lift as it pushes through the water. As the speed increases, the lift increases until planing is achieved. If the prop geometry is such that it creates stern or whole boat lift, it then reduces the planing speed by effectively reducing the force need from forward motion.

 

[SeanC]

Planing is a result of the reactive force on the hull producing lift as it pushes through the water. As the speed increases, the lift increases until planing is achieved. If the prop geometry is such that it creates stern or whole boat lift, it then reduces the planing speed by effectively reducing the force need from forward motion.

My question is can’t this stern lift be produced by trimming the motor or tabs. The fuel consumption will most probably be greater. In choppy conditions a prop with more bite will maintain speed and remain on the plane but a prop with less grip, the speed would drop and the boat would fall off the plane giving the feeling that the prop with more bite allows planing at a lower speed. I’m no expert. These are questions I have asked my self and it’s good to get other view on them.

 

[family affair]

My question is can’t this stern lift be produced by trimming the motor or tabs. The fuel consumption will most probably be greater. In choppy conditions a prop with more bite will maintain speed and remain on the plane but a prop with less grip, the speed would drop and the boat would fall off the plane giving the feeling that the prop with more bite allows planing at a lower speed. I’m no expert. These are questions I have asked my self and it’s good to get other view on them.

Yes, tabs and engine trim can help to lift the stern and plane at lower speeds, but the right prop provides even more lift allowing for the planing speed to be reduced further.
Yes, the props efficiency plays a part too. The prop efficiency drops as rpm decreased. This is where Sharrow claims to make an improvement although some other prop designs can have similar results. The Sharrow claims to have a better result across a broader range than other props, while also tracking better, quieter, and less vibration.

 

[SeanC]

Yes, tabs and engine trim can help to lift the stern and plane at lower speeds, but the right prop provides even more lift allowing for the planing speed to be reduced further.
Yes, the props efficiency plays a part too. The prop efficiency drops as rpm decreased. This is where Sharrow claims to make an improvement although some other prop designs can have similar results. The Sharrow claims to have a better result across a broader range than other props, while also tracking better, quieter, and less vibration.

That makes sense. Thanks.