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Alternator Mounting Failure

Jun 12, 2020
Hunter 410 Boston, MA
The alternator mounting bolt (bottom, pivot point) worn the hole in the gearcase cover so badly that the alternator is no longer stable. Caused the adjustment stud on the alternator to shear off. The spacer that fits over the bolt between the alternator's ears has a longitudinal crack. The alternator just about fell off.

Has anyone else had a similar failure? Any repair suggestions?


Feb 6, 1998
Canadian Sailcraft 36T Casco Bay, ME
That's not really a failure of mount/alternator/bracket it is a failure due to an incorrect installation and lack of routine inspection. If you don't provide more information including engine make, model and alternator make, model and amperage it is really not possible to give much guidance..

The correct repair involves removing the timing gear cover and having a machine shop repair it..
Jul 13, 2017
Hunter 410 Baltimore
More than likely the cause is that when the belt was tightened the pivot bolt was not tightened afterwards. The alternator will vibrate and elongate the holes. This is very common on large J180 alternators with two separate pivot mounting ears and separate bolts.