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kenstrom
Last seen: 2 months 3 weeks ago
Joined: 2/5/09
Posts: 65
Broken M-35B Alternator Bracket

I was in the process of changing out my water pump impeller when I found that my aluminum alternator bracket that secures the base of the alternator to the engine (Universal Part # 200436) was broken.  The aft ear that bolts to the engine was broken off.  Not sure how long ago this happened, but the alternator was still secured at the top to the other bracket that is uses to adjust belt tension and the belt was still reasonably tight as the alternator base was still resting and pushing up against the engine where the base bracket attaches to the engine.

I upgraded to a 90 Amp Leece-Neville alternator about 6 years ago, so the weight of the alternator is greater than the original.  I read the posts about making sure that you have the correct bolts used in the bracket (English vs. metric) but that was not the cause of this problem.

I have always thought my engine noise and engine vibration (which causes boat vibration and then more noise) was excessive, and am concerned that engine vibration is the main contributor of this problem. 

Has anyone else broken this aluminum bracket?  And, if so, did you find a cause and a potential solution to prevent this from happening again.  Having this happen in the middle of Lake Michigan would have been a major problem for me.

Thanks for any info or suggestions.

Ken

Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes

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Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes

pkeyser's picture
pkeyser
Last seen: 1 day 4 min ago
Joined: 5/18/13
Posts: 397

Ken-
Our boat also has an upgraded/larger alternator. The engine has about a 1000 hours and no bracket issue up to this point, but I will be diligent in periodically checking. Thanks for sharing your information. Do you have a picture to post so that we can see the failure point?
The M25 engines had issues and were addressed with a redesigned bracket, but I've not heard of any M35 issues- at least with the standard OEM alternator.

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Paul & Wendy Keyser
"First Light"
Newburyport MA/Rye NH
2005 C36 MKII #2257
Wing, M35B

Haro's picture
Haro
Last seen: 8 hours 6 min ago
Joined: 11/7/14
Posts: 240

Ken, my alternator bracket on M35B also broke into 3 pieces and the alternator still worked. It was hanging on from its upper bracket arm - amazing. I still have the original 51 AMP alternator.
See all of the images here http://mei1970.org/saillavie/c36Album/index.php?album=Alternator-Bracket
It is lucky that I was able to get 2 more brackets - one as spare. Engine hours are 1250
I asked if the new ones were improved - the answer was no.
The 2 bolts - in my case - were not broken fortunately.
My engine had been vibrating exessively, I thought it was due to worn out engine mounts. The engine now runs very smoothly and the belt does not bounce off the engine.

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Maine Sail
Last seen: 2 months 1 day ago
Joined: 2/26/10
Posts: 315

We've seen quite a few of this type bracket fail. In my opinion it should have been machined from steel not aluminum. The last one we did, I dropped the old one at a local machine shop and they duplicated it in steel.. One word of caution if the bracket "ears" do not fit rather snugly over the engine bracket, or alternator foot, these brackets really don't tolerate any bracket ear "flex" and this can lead to an early failure. If you're upgrading the alternator you may want to drop the old bracket at a machine shop and have it duplicated in steel. 

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-Maine Sail

https://www.marinehowto.com/

 
kenstrom
Last seen: 2 months 3 weeks ago
Joined: 2/5/09
Posts: 65

Here is a picture of the broken bracket.  Note the bolt broke also.  I assume the bolt broke after the bracket broke, and then a portion of the bolt worked its way out of the end of the threaded bracket.

Hope this makes it easier to see what happened.

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AttachmentSize
File Bracket Compress.docx22.76 KB
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Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes

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