Damage to the Alternator housing at the pivot point.

[VIKINGBEAR]

I came across some info about damaged alternator housing written by Stu Jackson, on a Catalina 34 website https://c34.org/bbs/index.php/topic,5127.0.html
As I have had some issues recently with adjusting the belt, this prompted me to take a closer look at my alternator, and, surprise, surprise; I discovered that I had the same problem on my Universal M25 engine as Stu had written about.
I believe that if I had not seen the problem now, I would have had a major problem on my hands. Thanks Stu!


Engine: Universal M25, Alternator, DELCO-REMY BE, 10 SI, 12 Volt, 51 AMPBelt size: Napa XL 25/7395 installed on the new type bracket.


Upon closer inspection: The large 9 mm pinion bolt holding the alt to the bracket, was not the right dia and was wobbling due to vibration. This caused wear and tear to the alt housing and if not corrected would eventually have caused the alternator to break loose. (see pictures below.)

A picture below is taken from the top and clearly shows the awkward angle of the alternator when belt is tightened, due to the damaged housing and wrong bolt. This again created lots of dust as well.


Understand that the bracket holding the alternator on most of these M25 diesels, are adjustable, that the slot where they are attached to the engine are made so the bracket can be slid fore or aft to get the proper alignment. This is not the case with my bracket, it cannot be moved.


However, I do believe the bracket is aligned correctly and that the problem was caused by not using the correct pinion bolt, and not using washers on the pinion bolt, between the bracket ears and alternator.


Took the alternator off and brought it to a local Alternator Shop who replaced the damaged housing with a used but good housing with a 10 mm opening for the pivot bolt. (Total only $ 30 including a test of the alternator)
10 mm is also the size of the hole in the ears on the bracket where the pinion bolt holding the alternator is.


I then purchased a 10mm bolt with corresponding lock washer and nut. This bolt is a tight fit and does not cause any wiggle. (The previous bolt was 9 mm which was the wrong size which caused this entire problem)


I also bought new 5/16” bolt for the bracket holding the adjuster arm. The bolt is longer than the old one and will have lock washer and nut on the back side (which the old bolt did not have) preventing slippage.

I then ran into another problem trying to fit the repaired alt housing back onto the bracket: Over the years of tightening the pinion bolt/nuts, the bracket was slightly bent inward, and the new alt housing was about 1 MM too wide.
It took a while to file the bracket ears sufficiently to fit the new housing. Needless to say, the alternator is now a tight fit on the bracket ears and the new 10 MM bolt fits perfectly on the bracket ears as well as in the hole on the alternator housing. See the last pictur below.

Mainsail describes this problem on his excellent website https://marinehowto.com/
He also states that “Universal engines are not the only ones that have improperly sized pivot bolts. MANY factory engines including Yanmar, Volvo/Perkins and Universal often ship with the wrong sized bolt for the alternator to pivot on.”

If not already done so, you may want to check your alternator carefully if you have any of these engines.

[Bycrick]

It seems to be a common problem when "mechanics" work on Yanmar engines. They are supposed to be 10mm bolts, but 5/16” are easier to find, so …..

The last time I had somebody working on the motor, he had to take off the factory alternator. A while later when reinstalling it, he asks me "have you got a couple of 3/8” flat washers?" When I asked why he needed them he showed me a stack of about a dozen washers that had been used a spacer on the alternator pivot bolt. He’d apparently lost several.
Upon further examination, not only were washers missing, but the bolt was the wrong size. But if he hadn’t lost some washers and had to ask me ……

[Lepke]

10si alternators are cheap at the junk yard or ebay if you need a new housing. Not hard to put your parts in a new case.