help noob with prop issue.

[DDM02]

Hello. I bought a boat with a messed up prop. The previous owner included a new one with the sale. I had the boat out with the old prop and it was perfectly fine to me. I went to replace it today and noticed the new one is smaller. Can someone please tell me if there are going to be any significant changes with the new smaller prop? I dont.know much about pitch ect. 1992 bayliner capri with the factory force 120.

Old prop




This is the new prop





This is both together, new one is on the right

 

[Frank Acampora]

Propeller pitch is like gears on a car. Higher pitch loads the engine more, like high gear on a car. The water acts like an automatic transmission. Higher pitch CAN mean more speed ONLY if the engine can adequately turn the prop at a good RPM. If the engine does not have the power, higher pitch will actually be slower.

Force engines use a nominal 13 inch diameter prop. Nominal means that diameter can range from high 12s to low 13s. In your case, the original prop was a 13 X19 . The new prop is 12 5/8 X 21 pitch. AS pitch goes up, the diameter is USUALLY reduced to compensate. In your case, I suspect that the 21 pitch prop will be a little too much for your engine. Most Bayliners I have seen come with a tachometer and speedometer. You need to check the RPM and speed with each prop. IF the RPM is within the 4500-5500 RPM range at wide open throttle, he engine is running correctly. If this is the case, use the prop that gives the most speed at wide open throttle.

As I said, I suspect the 21 pitch prop will be a little too much and if you intend water skiing it will definitely be too much. Depending upon your usual load and use, you may even need to get a 17 pitch prop to keep the engine in the 4500-5500 range. It is all subjective--you can not know until you see RPM

 

[DDM02]

Ok. Thank you for taking the time. I think I get it. I will just buy another one like the one that was on there. It worked great and I honestly didn't want to change it.

 

[Maclin]

You could have the 13x19 refurbished at a prop shop.

 

[DDM02]

You could have the 13x19 refurbished at a prop shop.

Yeah. I was thinking that too. But one of the blades looks like an S if you look from the side. There is also something that looks like a seal on the back of it where the spacer goes. It's rubber and looks ripped.

 

[Frank Acampora]

before you go buying another prop, TRY the 21 pitch--can't hurt. You would be surprised at how much damage can be repaired.

The rubber you see at the back is the hub. It is a bronze sleeve that has the splines and a rubber "donut" is glued to it. The hub is pressed into the prop and provides a little bit of "give when the engine is put into gear. It also provides a little bit of protection to the gears if you hit something.

And by the way: Do not "ease" the engine into gear this will wear thwe drive dogs. Correct procedure is to snap the handle quickly. There should be a thunk sound as the engine goes into gear.

 

[DDM02]

Thank you all for the help. I'm taking it to the local shop for an estimate tomorow.