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......
I found the same problem on my Universal M25 XPV. Someone had upgraded to a 100 amp alternator and substituted an SAE bolt for the original metric-sized bolt resulting in the sloppy fit and resulting poor alignment of the alternator. Lots of spray cans of belt dressing were found in the the boat as an additional insult. The belting arrangement was also the stock single A belt pulley. I replaced the bolt and reduced the alternator size to 60 amp to reduce belt slippage.