Re: 2003 90 HP Johnson prop question
4500 at WOT is killing that engine, you need to be up around 5500 to keep the motor from burning itself out.
4500 sounds very poor for that size prop to be honest, but maybe your boat is very heavy ???
first thing i would do is try a 13x17 prop, the 13 3/4 diameter is what is killing your set up, its too much prop diameter.
to use such a diameter is for inboards, much bigger outboards or very lightweight boats.
you might find that a 13x19 will give you around 5,000 rpm maybe a touch more, but i would first try a 13x17 and see the results.
you do need to get the max possible revs from the engine to get it to be at its most powerfull and best all round performance.
also by getting a 5500 top end you might see a bit more speed due to this one lugging the engine something realy bad.
its not even in the powerband at 4500 rpm.
try finding someone near you who can lend you their prop to try out, if its a 13 spline then have hundreds to choose from as the 3 cylinder engines use the same props as the v4 2 strokes with 13 splines.
once you get the right prop to give you 5500 top end, youl also see a huge difference in holeshot and much lower fuel bill !!!!!
the boat will be better all round for sure.
check how many splines and let us know what you have, you might have the larger 15 spline gearbox, but i doubt it.
phill