Higher AC frequencies are good for transformers, but don't have an effect on the
transmission of power reasonable distances and a boat is way smaller than that.
But since your AC is being converted to DC, the transformer argument is
irrelevant.

I'm lost - I have not mentioned transformers???

And your AC frequency will be pretty high start with -- there's more than one
cycle per rev.

Yes, a 10 pole alt at 8000 rpm is generating AC at around 1332Hz. More
A can be produced at 1332Hz than at 50Hz.