Prop advice

utfyrfytr

Petty Officer 2nd Class
Joined
Jul 14, 2014
Messages
185
I have a 1968 aluminum Crestliner Nordic 17' with a 1975, 115hp Merc, at WOT it runs at 30mph (gps) and 4200 rpm with two men in the boat. I don't care that much about increasing the speed but I would like to get the rpm's up closer to max which is 4800 - 5300. The current prop, and I don't know what brand it is, is an aluminum 13.25 X 17 and I was thinking about going to a 13.5 X 15. I think that will increase the rpm's but not sure if it will be enough. Any thoughts or other ideas? Thanks
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
A 15 prop will pull wot revs up definetly, but by how much ? If your combo is a heavy one expect at least + 400-500 wot revs going 2 less pitches. Only checkable on a wot test as loaded.

Happy Boating
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
In theory, dropping two inches in pitch will add 600 RPM. On your motor, it should also get you into a better power band, increasing the max RPM a bit more.

First I would verify all cylinders are working properly, and compression is good. The spark plugs should be dark brown to black. If any are white or real clean, you have some issues. Make sure the spark plug wires are not arcing to ground as well.
 
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