how fast should my 115 go

[Rienel]

I have a 18' Rienell deep v whith a 115 merc 6 (stack) and a 21 pitch prop. I had all kinds of tune ups done and can only seem to get max 28mph out of it. Is this ok? how fast should i be? my tack is not working but i don't seem to be reving to much.This motor was tested on a dyno and i was told it was working ok. could my prop be worn and i don't notice it? It takes me about 15seconds to get the boat up to plane as well. hte boat and motor are 1977 vintage<br /><br /> Tks

 

[Valv]

Re: how fast should my 115 go

Definitely a propeller pitch problem.<br /><br />Try a 19" or much better a 17" prop, it will give faster holeshot and probably correct RPMs, and speed.<br /><br />You will find a better answer if you install a tach, and see RPM, which should be no more than 5500 and no less than 5100