M25 Alternator Bracket Upgrade - SailNet Community

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Old 07-12-2011
Stu Jackson's Avatar
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M25 Alternator Bracket Upgrade

I thought everyone knew about this by now.

1985 Catalina 30 broken alternator brkt. - SailboatOwners.com
Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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Old 10-18-2011
eherlihy's Avatar
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Thank you Stu!!!

However, as I posted in the Ericson Owner's Forum (long story there...), the bolts included in the kit ARE WRONG!

Last year I installed the upgraded Alternator mounting bracket, and a new Leece-Nevile / Prestolite 90 amp alternator on my Universal M25. If you are reading this far, you probably know that the new alternator uses EXACTLY the same housing as the old 55 amp Motorola. BTW the kit is now ~$180.00

When I opened the box, I was happy to see that it included all the parts, including the Alternator mounting bolts.

I did the installation using the new bolts, but noticed that they did not seem to fit perfectly. The SAE Grade 5 pivot bolt allowed "a little" play of the alternator, and the tension bolt never seemed to fit "right." At the time I assumed that the alternator was machined so that the bolt would jam, thus preventing the bolt from loosening. The real reason is embarrassing....

I thought it strange that both of these bolts, and the nut were SAE.
031555 - 5/16NC x 1
031615 - 3/8NC x 3-1/2
031762 - Nut 3/8-16 Hex Steel Zinc

However, EVERY other fastener is Metric. I thought that Torrensen would know and include the correct bolts, however the extra play was because the bolts did not fit.

The Pivot bolt SHOULD BE a Metric M10 fastener. The tension bolt (connects the tension arm and the alternator) SHOULD BE a Metric M8 coarse thread.

I realized this because I was getting a little belt dust on the engine. After only 50 hours this summer, I thought that was unusual, or I would need to buy a lot of belts. I checked the alternator tension, and the "little" play seemed a "little" worse than it should have...

Because by now I had stripped some of the threads with the bolt that was included with the kit, I purchased a slightly longer bolt, a nut, and lock washer to use as a tension bolt. I also replaced the pivot bolt with a slightly longer M10 Fine thread bolt. It fit perfectly (no play at all). I used 2 nuts and a spring washer to jam the pivot bolt, so that it will not vibrate loose.

Lesson 1: If the components in the "kit" don't seem right to you, they are not.
Lesson 2: DO NOT USE THE ALTERNATOR MOUNTING BOLTS INCLUDED IN THE TORRENSEN KIT if they are SAE, and you have a Leece-Neville or Motorolla Alternator.
I did my upgrade in November of 2010. I addressed the bolt issue in October of 2011.

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USCG Licensed OUPV Captain, ASA 101/103/104/105/106/118 Certified Instructor - Also certified in Recreational Marine Electrical Systems
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Old 10-18-2011
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I just looked up the bracket kit from Catalina Direct. Catalina Direct: Universal Diesel Alternator Bracket Retrofit It is the EXACT same kit as the one from Torrensen. Therefore, these bolts are incorrect as well. But, it is $20 cheaper!
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