Alternator bracket cracked

[ELoverich]

I need some assistance in diagnosing an issue. I have a 1990 3.0L Mercruiser with an alpha 1 drive. The alternator bracket has broken three times now. I convinced myself that it was my fault(overtightening) however now that it has broken again after 7 hours use, I believe I have other issues. Has anyone had experience with this issue? I have read a lot(on this forum) about vibration could this be the problem? Please let me know.

 

[Don S]

Re: Alternator bracket cracked

Do you have a miss in the engine? Have you checked compression, done a complete tunup an such? Would you know if it was missing or not???
I've had many customers tell me there engine ran perfect only to find out it had 1 or more cylinders NOT firing, or no compression.

 

[wire2]

Re: Alternator bracket cracked

I bought a new Glastron back in '74 with a Merc 120 I-4. I installed an hour meter in an aluminum bracket on the main breaker support. At 214 hours the (apparently normal) vibration had totally disintegrated the innards of the hour meter.
I'm thinking your bracket may be "ringing" in resonance at certain rpm's. Can you have someone put a hand on the bracket while you slowly increase rpm? The vibration may become stronger for specific frequencies.

 

[ironhorse]

Re: Alternator bracket cracked

make a new steele one

 

[Coors]

Re: Alternator bracket cracked

Put a straight edge on the face of the pulleys, ans see if the line up, perfectly.