Posted by simpsonbrian1 on 07/25/17 - 10:28 AM
#1
Hi all,
I have a 1989 super sport 13' whaler with a new Merc 9.9hp pro kicker engine on her with a 4 blade prop. When at 3/4 throttle all seems fine. Anything more than that the engine rpms rev higher, but i do not get anymore speed out of her. seems like there is cavitation possibly. According to articles i have read, the motor is the correct length, cavitation plate just below the bottom of transom. Should i try a different propeller? Thank you in advance.
Brian
(fixed typo in model name)
Edited by Joe Kriz on 07/25/17 - 11:45 AM
Posted by jgortva on 07/25/17 - 1:14 PM
#2
simpsonbrian1,
I don't want to ask stupid questions but here it goes:
1) Is the tilt lever on your motor locked in the down position. The reason I ask is that I had a similar situation and discovered the trim on the motor was not locked down so at higher RPM, the outboard was slightly, "floating higher, thus making the prop cavitate.
2) What advantage is using the kicker at such high throttle? I find it hard to believe that it takes that much throttle to get to trolling speed.
Jim G.
Posted by gypsmjim on 07/25/17 - 6:14 PM
#3
If that is your main engine, it is too small for that hull. You are maxing out at hull speed. If it is your "kicker", its too big for the hull. A 6 HP will still max out at hull speed without the overkill.