Recommended RPM range on a yamaha?

[mahharhja]

Hi ALL !! i have a v4 130 yamaha motor on a 16 ft marshan v bottom boat. im currently using a merc vengence prop. which runs at 51mph on a gps at 5900 rpm. I need the best pullout for race skiing and the skis i pull are heavy so im looking for a little more speed while keeping my current holeshot. The spec for my motor says peak power at 5500 rpm but max rpm permittited is 6000rpm. Is there any benifit by dropping the pitch so the motor runs at the peak 5500rpm? or what about going over 6000rpm? All advise greafully recieved ;) Andy

[mahharhja]

<img src="http://nycz.us/is.php?i=5869&img=marshan16.jpg" border="0">

[mahharhja]

<img src="http://nycz.us/is.php?i=5871&img=driving_seat.jpg" border="0">

[Ray Neudecker]

Repitching to lower the rpm's may give a MPH gain but at a loss of hole shot. The motor will run very happily up to 6800 Rpm's, but you have a limiter which will hit about 6000-6100 RPm's.

[mahharhja]

Thanks for the fast reply Ray!! well the prop is a standard 18p vengance as ive said. ive tried a laser of 21" and was worse in every aspect :eek: one good prop was a 20p chopper and that had me upto over 55mph but no way could it pull out skiers!! what style of prop would you suggest as a start guide 3 or 4 blade. i need stern lift ,not bow lift as its on its tail when i pull a race skier out of the water!! i know im in a hard situation trying to get best of both worlds!! as and idea i could go a higher pitch say a 21/22p and fit large trim tabs for the holeshot. what do you think?:)

[Ray Neudecker]

I would start by installing a BOB's Machine Shop tail on and see about raising the motor. Watch water presure. I would disconnect the limiter and see what I had then. I would also remove every ounce of weight feasible from the boat.

[Markus]

For maximum life time of the engine, I would keep it at 5800-6000 rpm. If run at WOT too close to 5000 rpm, the wrist pin will eat into the piston.

[eli]

put on a merc hi 5 18 pitch on ,that laser prop is the worst one of the bunch.