1999 Catalina 36 MKII
I had noticed that the engine vibrated when I purchsed the boat in 2009. I got used to it thinking it was normal. I had noticed that the belt was hitting the engine creating black dust as a result of the engine vibration. It was years later during a long engine sail that I noticed the tachometer would vary quite a bit, I was not sure why that was. After I reached port and tied to the dock as a regular engine checkup I discovered a large piece of metal in the bilge under the engine. After close inspection I noticed that the alternator was hanging to the engine only by the belt adjustment bracket. The tac abnormal display was a s a result of belt slippage.
I replaced the bracket (part number 200436) with the original Universal bracket and returned home after a week. I noticed no vibration and the belt was not hitting the engine any longer. I was convinced that the alternator bracket was cracked when I bought the boat causing the vibration.
A few months later I noticed that the alternator was not charging the batteries. The cause of the failure was that the heavily painted inner surface of the newly installed alternator bracket bolts provided poor ground. To avoid this problem again I installed a #8 grounding cable from its ground lug to the shunt near the house batteries. The new Alternator is painted red instead of the expected silver paint.
All is well. The 51A alternator ( part No 041017) has put out as much as 31 Amps to charge the house batteries. The original alternator output voltage was 14.4 volts; the new one is 14.2 volts.
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