Problems with 65hp Mercury (boat won't move past a troll)

[Raven Blayde]

Hi everyone! I just joined up here and hopefully can get some help with this new "Nightmare Project" lol... I recently bought an early 70's model boat, motor and trailer (15ft fiberglass with a 65hp Mercury on the back). This is my first boat, so I know NOTHING about them. The engine starts up and sounds good. I put it in the water for the first time monday and took it for a spin. As long as I go VERY slow (like trolling speed) everythings fine. Soon as I give it some throttle and try speeding up, the engine revs up, but the boat slows down. If it was a car, I'd say the transmission was shot. lol.... So, I did a bit of reading here and found that others have had simular troubles with their motors that was caused by a bad seal or hub at the prop. I pulled the bottom half of the motor apart to have a look and right off the bat, I found that the top of the large shaft (that runs from the motor to the lower part) had the teeth of the gears worn very badly on one side. I'm betting this is a bad sign to start with. Now I'm sitting here trying to decide whether or not I should try fixing this motor, or just buy another. The shafts I found for this thing were close to $300!! OUCH!!! And this may not be the only problem the motor has either! I may still have other parts to replace in the lower part once I get it apart and see what's there. Just not sure what to do here. Like I said though, as far as the running part, the engine starts right up and seems to run fine. It just won't go any faster than trolling speed. Is it worth fixing? Thanks in advance

 

[jebeebe]

Re: Problems with 65hp Mercury (boat won't move past a troll)

Are you saying the spline on the end of the drive shaft is worn? Your problem sounds like the prop hub is stripped. That could be fixed with a used prop. The rubber hub in the prop can slip under power. If it is the spline slipping in the power head I would think it would think it would make an awfull racket. Sounds like some more trouble shooting is needed...............Jerry

 

[Raven Blayde]

Re: Problems with 65hp Mercury (boat won't move past a troll)

Thanks for the lighnting fast reply Jerry! I didn't notice any unusual noises coming from the motor under load, so that drive shaft might not be the issue then. The teeth look pretty worn on one side to me, but maybe this is normal wear? Heck, I don't know anything about boat motors, so I'm not even sure what half this stuff is that I'm looking at (I'm pretty decent at building car engines though) lol...

 

[jebeebe]

Re: Problems with 65hp Mercury (boat won't move past a troll)

I'd try another prop and see if that does it , if not then progress further