Mercruiser 5.7 EFI alternator bracket keeps cracking

KHE

Member
Feb 28, 2012
238
West Michigan
Boat Info
1997 Sea Ray 240 Sundancer
Engines
Mercruiser 5.7L EFI alpha 1 Gen 2 drive
Background information: Three years ago, I noticed my volt meter at 12 volts while cruising. The issue was a broken terminal on the lead to the battery. Fortunately, there was no damage to the alternator. I noticed the mounting bracket was cracked through and the alternator was vibrating. I had no idea how long the bracket was cracked prior to the battery lead terminal breaking.

I removed the racket, welded it, and reinstalled it. Everything was fine until yesterday. I cleared the pierhead into Lake Michigan and noticed the volt meter was at 12V. I shut everything down and inspected the alternator. The battery lead was broken off the terminal and the alternator mounting bracket was cracked again.

I repaired the terminal while on the water and the system was charging so we were able to complete our boat ride. Tomorrow, I plan to remove the bracket and weld it but can't help but wonder why it keeps cracking. After welding it, I may add some steel plates to reinforce it but there has to be something else causing the bracket to crack. The original lasted 20 years but the bracket is no longer available from Mercruiser. I can find a used one but can't get the question out of my mind" Why did the original last 20 years but the repaired version barely makes it to three years.
 
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