Alternator opinion

I had a problem with my alternator not charging my battery so I had it tested at the local auto parts place. Sure enough, the alternator was not putting out anything.   I took it to the local alternator rebuild shop and he confirmed the same thing. He noticed right away that it was a marine alternator, 37 amp, price to rebuild is $100. Ok, pretty simple. I called today and he said it's done. He also said they offer a 100 amp single wire direct replacement marine alternator by Delco that he will sell me for $125 and I leave my old alternator behind.   He said the Delco is brand new, not rebuilt, bolts in exactly the same as current alternator, and only 1 wire hook up. He said there is a spot for a ground if you want one.

I'm not running a stereo and the only aftermarket equipment I'm have is a heater. It’s only $25 extra, so I guess the question is, do I need the 100 amp vs. the 37 amp? Has anyone done this swap, and what do I do with the 2 extra wires. (I didn't think any of the existing was a ground.)

Thanks for your thoughts.

There is a small concern in that the 100 amp alternator may require you to upgrade the one wire, and possibly your main circuit breaker. The reality is that with most batteries and no heavy engine loads you will not ever trip your circuit breaker as the max current will be limited by the internal resistance of the battery. However with a severely discharged battery it might occur that you will trip the breaker, at which point the boat will act like you have removed the battery while running.   Your voltage will spike (putting things like electronic ignition modules in jeopardy) and when you turn off the boat it won’t restart until you reset the breaker.