Performance issue with Alpha I outdrive

Izeman0302

Recruit
Joined
Jun 15, 2019
Messages
2
1988 EBKO Monte Carlo bowridet
Mercruiser 3.0 4 cyl., Alpha I outdrive

Had boat out on the water to test the engine after repair. Was running great and was up to full throttle. There was a loud plunk and the boat/engine slowed sharply and the engine stalled. Once started it ran very rough through retrieval. Got home and found the exhaust bellows blown apart. Replaced the part and the engine ran good but sounded loud at the outdrive. Took the boat back out on the water and the same plunk sound and there seems to be a "drag" that holds the boat back at any engine rpm. Engine appears to be running fine so the problem seems to be the outdrive.
I don't know enough about outdrives to guess at this point and the only suggestion from my engine mechanic may be the U-joint may be freezing up?
Thanks
 

TunaFish389

Petty Officer 2nd Class
Joined
Apr 26, 2018
Messages
184
Sounds engine related. The blown apart exhaust bellows point to a running rich/a cylinder not firing. Unburnt gas that ingites in the exhast system.

That drag might be timing or down a cylinder. I would spend my time on the engine. I don't see the drive blowing apart an exhaust bellow.
 

Izeman0302

Recruit
Joined
Jun 15, 2019
Messages
2
The engine is running smooth (no misses). And this last time out the new bellows remained intact. In the boat the engine is smooth and quiet, behind the boat is where it is loud.
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Southtowns27

Seaman
Joined
Jun 16, 2013
Messages
73
I agree to focus on the engine. Sounds like the timing could be late or it's down a cylinder
 

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
Pull the drive and put a hose in the water inlet so you can run it. If you still have the noise it is in the engine.
 
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