prop theory help please

[ohbenito]

hello venerable boating wise folk. i have a bayliner capri with a seahorse 150 running a 15x17. a friend gave me a sweet 14 1/4x21 stainless prop. I would like to ask please, what effect switching to the 14 would have. in english please. the slip coefficient and inverted drive ratios in the prop calculators have served only to help get me further than completely lost.
thank you,
ben

 

[Oldskool]

Re: prop theory help please

You can generally figure on decreasing your WOT (wide open throttle) RPM by approximately 200 RPM per inch increase in pitch. In your case, that would be around 800 RPM. You don't mention what your current WOT or recommended WOT is. But unless you are seriously able to over rev this engine, then this prop is likely to be too aggressive for your boat. You want your engine to be able to operate within the recommended WOT range to prevent lugging the engine.

 

[junior1113]

Re: prop theory help please

ditto, you will likely be under proped. leading to lugging and eventualy killing that old one. need to be seeing at least 5500 wide open rpm. hole shot will suffer and top speed would be same at lower rpm. 2 strokes live on rpms dont decrease them

 

[ohbenito]

Re: prop theory help please

thank you for the help. the prop stays as is. i will fight shiny stainless-itis.