I used all Forespar Marelon seacocks, the triangular flanged ones, 4 below the waterline, and one in a sink drain slightly above the waterline. The one in the sink drain froze open, I tried lubing it as much as was possible but with little improvement. I called Forespar for ideas, their attitude was ya, if you don't exercise them regularly they do that. They also said that there is no fix other than replacement. Their attitude was just buy another one.
The ones below the waterline still work, but now I'm just holding my breath waiting for one of those to freeze, knowing that would entail a haulout and a whole bunch more work to fix.. When I replaced my thruhulls I was all excited to use all Marelon,no corrosion and all that. After my experience I'm less enthused, after my conversations with Forespar even less.
Another thing which I think is a big drawback is that there is no way to lube the ball other than squirting something in the ends, seems like there should be a grease fitting in the side or something.
Here is a serious weirdity. On the Forespar Marelon triangular flange seacocks there is no specific orientation between the flange bolt pattern and the valve lever. I found this out by using one seacock as a pattern to drill the mounting holes for all my seacocks. Then when I went to mount them the handle directions were all over the place. I called Forespar on this also, they said it's correct that there is no specific orientation between triangular flange and lever. They have multiple molds and they're all different. That one I really don't understand.
If I was to do it again I don't think I'd use Forespar Marelon again. Seems like a good idea but I think the execution is lacking.
This got me thinking. Whatever happened to that Tru-Design line of glass filled composite thruhulls that Raritan picked up? It doesn't show up on their website anymore. Looked like nice stuff, Raritan is a great company. I think Tru-Design is out of NZ and originally it was all metric, I thought they then added imperial.