If you have the original starter...pull it and take it to an auto/electric place and have it rewound and reworked. I had my starter for my Perkins 4-108 rewound and reworked in less than 48 hours in Ft. Myers, FL. And it only cost me $78.00 and it works like a charm and they replaced the solenoid and painted it as well.
My last boat which I had for twelve years had an Atomic 4. Most of the bolt-on parts were standard automotive items. Ditto for the starter. Removed it and carried it into the nearest supermarket-type auto parts store. Matched the bolt pattern with a model they sold, and merely checked the numbers and capacity. Took about six hours and it is still working fine now after seven years. The project would have taken less time except for having to cut a wrench in half in order to reach one pesky mounting bolt.
Marine electrical power components should be ignition protected to prevent them from being the ignition source (open spark) for an explosion or fire of the accumulated vapor thay may be in the bilge. Sure, standard automotive starters & solenoids will work and are real cheap in comparison to totally enclosed non-vented marine versions ... but non-ignition versions can make your boat go BOOOOOM. There''s a REAL difference (frame construction) between totally enclosed non-vented and vented automotive starters, etc.
The starter that I installed from the auto parts store was non-vented, and nearly matched the original one installed in 1973. Perhaps I was too simplistic in my explanation, and I certainly do not want someone else to create an unsafe condition. These same Universal built motors were also used in a lot of land uses, primarily construction equipment where they were non-vented because of dust and dirt. Suitability for marine use, and somewhat enclosed compartments, is worth looking into, and I apologize for not mentioning that. Prstolite sure sounds automotive.