I would be very hesitant on adding to the load on my outboard alternator. Unless you are running for a couple hours to and from your fishing spot, you will not be getting much of a charge. Probably every time you go out, you will be forcing your outboard alternator to work at max capacity. That is a quick way to shorten the life of an alternator. A quick check on EBay used alternators for my Optimax running about $270 us. I keep my boat at my off the grid camp, and use my 1000 w Honda inverter generator to charge the batteries as we are watching tv or just running the generator for any reason. I have an onboard 220 that does just fine and I charge the batteries (2 can tire group 24) every night if I can. No issues. My opti is a 2005 and same alternator.