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Author Topic: M 25 alternator spacer  (Read 3040 times)

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M 25 alternator spacer
« on: June 24, 2012, 07:25:53 PM »

I snapped the 3" bolt on the alternator adjusting arm. When I looked online, there is supposed to be a spacer behind the adjusting arm. I can't find it for much less than $50 !!! Does anyone know the size/specs of this spacer?

Jerry S     
Pleiades  hull #1076
There is NOTHING--absolutely nothing--half so much worth doing as simply messing about in boats.    Kenneth Grahame

Stu Jackson

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Re: M 25 alternator spacer
« Reply #1 on: June 24, 2012, 08:43:38 PM »


I'm not too sure about your question.

The 3 inch bolts need to be metric or else your alternator WILL wobble.  Not good for the belt or the bearings.

From the C34 Tech wiki:

I bought the metric bolt, makes a BIG difference.  Maine Sail has written it up, too.

A spacer for $50?!?  Can't you use fender washers?

Can you be more specific?


October 2011 - From E. Herlihy an O'Day 35 owner: Last November (2010) I installed the upgraded Alternator mounting bracket, with the kit available through Torrensen Marine, and while I was at it I installed 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 containing the kit, 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 assumed that Torrensen would know and include the correct bolts, however the extra play was because the bolts did not fit... you know what happens when you ass-u-me... 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. In October of this year (2011), 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. I can't speak to the kit available through Catalina Direct, but the Torrensen kit has the wrong bolts!

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 Motorola Alternator.
« Last Edit: June 24, 2012, 08:44:14 PM by Stu Jackson »
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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Ron Hill

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Re: M 25 alternator spacer
« Reply #2 on: June 27, 2012, 05:28:40 PM »

Jerry : The bolt that goes thru the alternator case is an SAE bolt (for the M25 & M25XP engines).  The hex head is 9/16".
You want to make sure that you get a bolt that is NOT threaded thruout.  The non threaded portion of bolt should be all the way thru opening bracket hole, with just enough thread to go into the end with the threaded hole (for strength and less wear).

You can use a stack of washers to take up the slack for awhile.  You really want to go to a machine shop and have them drill a hole in a piece of round stock and cut it to the length of you washer stack - that really helps lessen vibration.  The cost is minimal and you'll then have the correct spacer.

A thought  
« Last Edit: June 28, 2012, 02:18:00 PM by Ron Hill »
Ron, Apache #788
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