Re: Gen-set vs. engine
Small loads? I would also suggest the battery bank should be able to carry those. You probably need to look at the complete power system so see what is "reasonable" versus perhaps what was done wrong, or done cheap when the boat was put up for sale.
In a perfect world, you have the genset, use it. Maintain it, use it up, whatever, but if you are using the main engine instead of the genset--then the genset shouldn't be there. If you actually can price out the long-term maintenance on the main engine, including little problems like carbon in the exhaust elbow caused by extensive running at low rpms, the genset damn well ought to come out cheaper, including whatever maintenance it might need. If it doesn't...trash it.
But a coffee pot, a hairdryer...these things should all be insignificant loads to the battery bank, on a boat that's big enough to be carrying a genset as well.
Is there a power monitor on the boat, to show you total watt-hours in and out of the battery bank? That might be a good place to start.