I have a family fish/ski boat. It has 2 Group 29 batteries (...or maybe they are 27s, I can't remember). It has a plug in the front of the boat for me to plug in my trolling motor (which runs off these two engine batteries). It's never been an issue for me (low batteries). Assuming I zoom too and from the fishing spot on the water, the engine alternator seems to have enough time to keep the batteries sufficiently charged.
Just recently, with my boat sitting for many months in winter storage, I decided I wanted to put a little portable solar on the boat to keep the batteries topped off during the winter. I bought some used 100w panels for $25 each and created a quick and easy portable charging system for my boat (using one 100w panel). (Side note: Has anyone else discovered solar to be a bit addictive??) It got my batteries up to 100% in no time at all (...they weren't low to begin with). Honestly, I find myself keeping the whole system unplugged most of the time because I don't want to just leave the batteries for days/weeks/months with a trickle charge on them when they don't really need it.
My boat has a ski tower. I usually take it off when I'm fishing (if there is more than 2 people). But if not, I could easily mount 1-3 panels up there. It would even provide a little bit of shade underneath. That would keep my trolling batteries charged up all day EVEN WHILE USING THEM. So....perhaps you can find a convenient (or creative) way of mounting 100-200 watts of solar on your boat. If you don't have any space on deck or on top of a canopy, maybe you could mount it on an 8' tall pole somewhere to keep it out of the way.
Perhaps this is all just a crazy idea...it's late (lol)
-Chris
