Just like the image above do not trust the alternator ear, soft aluminum, to hold the adjustment arm tight. Buy a longer bolt so you can put a backing lock nut on it.. Here I am using both a split washer and a nyloc nut.
Over the years I have really come to despise stamped steel pulleys when trying to drive serious current. Whenever I can source a billet machined pulley I do. These pulleys seem to work best under high loads.
The belt pictured here is also one of my favorites, it is a Dayco Top Cog. When I can't source a Dayco Top Cog I usually use a Gates XL. These Gates belts are sold nation wide by NAPA as the NAPA Premium XL Belt.
Sloppy Factory Bolt Fit
Oh no trouble in Paradise! Caveat emptor or DO NOT always trust that the manufacturer has taken the time to do things right. This is an utter embarrassment to the folks at Westerbeke and is plain and simply SLOPPY, especially when this "upgrade" is supposed to address deficiencies in design and installation.
I spoke with Bob B. at Westerbeke about this at the 2013 Annapolis Sailboat Show and HOPEFULLY they have now addressed this issue. Still be on the look out for sloppy fitting pivot bolts. The Devil is always in the details.
Many owners of the M-25's have alternators as large as 100A or more on these engines. Install an alternator with a sloppy fitting pivot bolt like this and you are asking for trouble. The alternator will have chronic alignment issues and will eventually oblong the pivot hole in the alternator thus potentially ruining the case.. SHAME ON Westerbeke!
The bolt passing through the alternator ear AND the bracket MUST be a proper fit. This is NOT a proper fit..
Factory Bolt & Replacement Metric Bolt
The factory sloppy fitting bolt on the right and the proper fitting bolt on the left. Oh and no Westerbeke did not reimburse me for the 1 hours time it took to go to the hardware store and do their job for them!! Such is life......
Proper Bolt Fit
This is how the pivot bolt should fit.... I think I wound up with an M10 X 100mm metric sized bolt, but please don't take that to the bank. I am only human and with my aging memory can't remember every little detail and I did not write that one down.
If the alternator pivot ear and bracket holes are not the same size or do not match, over drill them until you can get a proper matching fit. For the alternator it may be best to drop it at a machine shop so you know the hole is straight.
Why Does Proper Bolt Size Matter?
I think this image sums it up. This owner had the wrong size pivot bolt and this was the result!
Image courtesy: S. Jackson
Other than the bracket, adjustment arm and a short piece of curved radiator hose this is what comes in the upgrade kit. You will need to re-route the cooling hose but this can be very boat/engine room specific as to how you do it.. The copper elbow is used for that purpose.
You need four longer manifold studs and they send you four... I would advise ordering two standard ones when you do this as it is one of those Murphy's Law things; "While you're in there" might as well replace them.". If you don't one of the old ones will certainly fail on you next week... (wink)
Alternator Bracket Installed
Here is the finished installation. All you will need to do is re-fill the engine with antifreeze and purge the air from the system.
This engine uses a Gates XL 7390 belt and yours may too depending upon your alternator pulley. The 7390 is a good place to start.
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