The jury is still out, but here's what I have so far. I installed 2 x 120 watt Mitsubishi solar panels (MF120EC4)- the ones recommended by Wholesale Solar for RV/Marine use. They fit perfectly on the sports rack using the RV mounts they have available along with an aluminum backing plates I made. I also installed the Morningstar Prostar PS-30 (30 amp) controller. A bit of overkill, but I wanted the gauges to see what power was being generated.
The installation instructions that come with the Mitsubishi panels say that they cannot be used within 500 meters of salt water. That was a surprise to me, and to Wholesale Solar. The Prostar says for acceptable life expectancy, don't subject it to a marine environment. I contacted Mitsubishi, they confirmed the corrosion portion of the warranty is void if the problem was caused by salt water. I am waiting to see what Wholesale Solar says, but I don't expect much. I contacted Mitsubishi again - to find out what corrodes and maybe try to prevent it. We'll see what I learn, if anything.
In the rain, with the panels away from the sun, I got ~ 4 amps charging the batteries. When the sun came out, I got 6-8, and when I rotated the boat so the stern was aligned with the sun, I got 8-10 amps (at 11am). The two panel combined rating is 13.6 amps at 17.6 v. The batteries were fully charged at the time, I don't know yet if that makes a difference.
If I only get 4-5 hours of 4-6 amps, that will be roughly half of our daily consumption (I think). That's mostly refrigeration. I hope to get twice that - and still am hopeful. I have 4 x 100amp (group27, maint free) house batteries, so have 200 amphrs to consume. Without the solar, I think I have 4 days of battery power, if I only get 25 amphrs/day from the panels - that will give us 8 days at anchor. If I get 50 amphr/day, we'll start thinking about a water maker 'cause we may never have to leave.
More later,
Mac