This post is about an alternator installation I installed a long time ago, 1998, on a Catalina 36.
This boat was originally outfitted with the stock 55 Amp internally regulated Motorola alternator. The future system was to include an update to the house battery bank for more total amp hours. If I increased the capacity I knew the stock alternator would certainly be maxed out.
This picture shows the alternator I used and it's sales and model number. I chose this alternator, over some others, because it was the only one using the identical case size that the original stock Motorola did. Leece-Neville also used to build many of the alternators for Balmar and they build decent little alternators.
Frustratingly I soon discovered there was only one unit available from Balmar that was a exact case fit on the Universal M-25. It is called the Model 81 but cost nearly $600.00 and was virtually identical to the Leece-Neville 8MR series. At the time however it was not available which meant using another "close enough" Balmar unit.
Not using an "exact fit" on this engine could mean a trip to the machine shop for a custom bracket to accommodate other units with slightly different cases. I did not want to do this. Having installed a fair number of marine alts I recognized just how difficult it is to align a non-direct fit alternator with custom mounts. When these alternators pull that kind of amperage it becomes very important that the pulleys line up.
I decided that taking the Balmar route would be more trouble & expense than it was worth to make if fit correctly. I certainly did not want get involved in modification of the alternator brackets or get into custom welding so I chose the Leece-Neville as a direct, bolt on, fit.