need a different prop. 40hp yamaha

[dschroeder]

1988 40hp yamaha 13ft addison addictor (see pics) cross between a V hull and trihull

current prop is a 3 blade aluminum 13" pitch 10.5" diameter

WOT rpm was only 1500 with 2 of us in the boat. engine just tuned up and carbs rebuilt...boat won't get up on plane, tried adujusting the trim position pin through all 5 holes, performed slightly better with the engine trimmed out.

yamaha says engine should be around 5500rpm max at WOT...

what should I try for pitch? stay with 3 blades or go to 4 blades?

 

[pootnic]

Re: need a different prop. 40hp yamaha

That little boat can't be that heavy...can it?
I think theres a setup problem or the motor still isn't working properly.
How far in the water does the motor sit?(anti-vent plate)
Seen one of those boats on Auction hunters(tv show)the other night,with a 25hp and with a real big guy,planed out fine.Although it did have a "fin" atttached to it,maybe that will help you.
Did you try it alone,I think it should plane out with that pitch, if set up right.

 

[steelespike]

Re: need a different prop. 40hp yamaha

Has the boat allways had the 40 on it?I would suspect the motor isn't running right.
At 1500 rpm and unable to plane I would suspect that it isn't running on all cylinders.
Pull the plugs and note their position(cylinder) and condition.Be sure the throttle opens all the way.You wouldn't be the first not to realize a motor was missing one or more cylinders.