Some possibilities
That boat comes with a stock 50-amp alternator. At 2800 rpm, it should produce at least 40 amps. Four hours of running means 160 amp-hours. That's not a lot of amp-hours. The crummy little batteries that the original owner replaced probably held about 160 amp-hours total. I'll bet the previous owner had a slip with shore power. That's what I use to charge up my 380 amp-hour bank. If I had to rely on the alternator alone... well, you can do the math. You are likely keeping your boat on a mooring or at a slip w/o shore power. If you're going to keep this battery bank, you need to find some alternate power sources. Solar cells are steady producers of electricity, but you'll need a lot of them and they are expensive. You'll also need to leave most of them at the dock, since there aren't a lot of places to install them on a 33-foot sloop. A wind generator is the best choice. A generator is harder to install than solar cells, but it will make enough juice to keep your batteries charged, if you're a weekend sailor. Or, you could go back to the smaller bank. But if you have a fridge, you won't be able to run it, or will have to ration its operation. Even a 100-amp alternator wouldn't be the best solution, unless you want to spend your tranquil hours at anchor watching diesel fumes come out the back of your boat. Paul sv Escape Artist h336
