I’ve personally had better luck with Kohlers than Westerbekes. I would suggest you research extensively before purchase.

I've had Kohlers, Onans, Westerbekes, and "Mercruiser" gensets. They are all decent units.

You would be best off if you could get your hands on the original generator.

You CANNOT put a portable generator in an enclosed area. Period. Highly illegal, highly dangerous, likely fatal to somebody. There are also plenty of regulations that prevent the use of a non-marine generator even if it is sitting on a swim platform. BUT lots of people do that, and so have I in the past.

But you can buy used generators. Plan to replace any bearings and brushes in the power end, and do a leak down test on the motor side, and get an oil analysis on whatever comes out of the crankcase.. Make sure the raw water pump is in an accessible location when installed in your boat OR move it to a good location. You will need to replace the impeller every season or so.

I can't imagine what was so bad on the original generator that it had to be scrapped. Even if the motor was shot, a short block is a whole lot cheaper than a new genny.