4.3 Mercruiser has a clunking sound and won't go into gear

bjungers said:

I just bought an inboard boat, used to have an outboard. I have a 4.3 Mercruiser with an Alpha 1 outdrive. I don't know much about inboards so I was wondering if I could get some help. Last Saturday we were out on the lake just cruising around. I was going at just above idle and all of a sudden I heard a clunking sound and we stopped. Now even when it's not in gear the engine has a grinding/clunking sound and it won't go into gear. I can feel the vibration throughout the entire boat. Someone told me it could be the throttle cable, but I can see the cable move when I put it into gear. If I have it in forward I can spin the prop clockwise, but not counter clockwise and vise versa in reverse. Is this something in my outdrive or the actual engine? Is this hopefully something I can fix myself or not? I don't have a lot of knowledge of outboards, but I'm not completely mechanically stupid. Any help would be great.

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bjungers said:

Well I took off the lower unit and the seals and and the gasket were absolutely ruined. I realized that this was not the problem, but it didn't help it. After looking closer, the spline (i think it's called a spline) that the drive shaft goes into looks completely smooth. This would make sense why the boat would have a vibration to it. It almost looks like it is made out of plastic. Is it very easy to replace this? Any help would be greatly appreciated.

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Bond-o said:

Ayuh,.... That's the Coupler, it's bolted to the flywheel,....

Not to bad a job,... once the motor's out....

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