Help What Prop????????????

lyncraft_mechanic

Petty Officer 1st Class
Joined
Jun 22, 2007
Messages
233
I have a 2002 40hp johnson outboard with a 11 3/4 x 17 prop mounted on a 14' fiberglass boat, here is my problem I only get about 25mph out of it. Should I change props, would this make a difference?
I posted a simular question, and was told that I had a 31% prop slip and that there was nothing they could help me with with out my rpm readings!! since then i have installed a tachometer and here are some numbers: at idle 800rpm, wot with the warmup 4000 rpm and wot in gear 3000rpm. I was also told that this engine should be 5500 rpm at wot, any suggestions?
 
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