RPM change with smaller prop

[Plainsman]

I have a 19in prop that is getting close to 4800 RPM at WOT. I was given a 15in prop and was wondering how much that would raise the RPMs.

Also, the 15in is vented (is that the right word when the prop has holes in it?)

Manul says 5000-5500 for the RPM range.

This is on a 17ft fiberglass runabout.

 

[walleyehed]

Re: RPM change with smaller prop

in theory, it would put you in the 5600 range, but prop design and engine torque curve can change that either way...5600 would be OK, but a bit more is better.

 

[Plainsman]

Re: RPM change with smaller prop

Thanks Kenny, any idea how much speed I might lose?

 

[walleyehed]

Re: RPM change with smaller prop

If we get the RPM up where it should be, and depending on blade design, the speed may stay the same, and in some cases, it can increase.

 

[Plainsman]

Re: RPM change with smaller prop

Well I put the 15in prop on today, but it doesn't go on as far as the old one did. The splines seem to line up. What would cause this?

 

[walleyehed]

Re: RPM change with smaller prop

It "may" require a different thrust washer...can you give me a P/N of the prop?

 

[Plainsman]

Re: RPM change with smaller prop

The number is 48 77342A4