Most all boat lifts are built from aluminum pieces, just like an erector set, and the very hot & humid summer of 2010 was the mother of all NH summers for growing mildew and yucky black mold. Boat lifts being situated next to a dock and close to shore are subjected to lots of water-wave action so it all combines to turn the aluminum surfaces into easy holds for the black mold to get a grip onto the flat aluminum horizontal surfaces.
If you are really looking for something to do, while you wait for your next quarterly dividend payment from BP Oil to show up, it is not a bad idea to remove your boatlift to the nearby shore, and clean/kill the black mold with a bleach solution either with a pressure washer or just scrubbing with a big sponge and rubber gloves.
For treating the non-aluminum parts such as steel cross supports, there's an aerosol $6 can of metal maintenance-treatment for farm and garden equipment that penetrates into steel and is a good protectant. It contains stuff like penetrating oil and a liquid wax coating. Heath's Hdwe in Center Harbor carries the stuff! Canuaba car wax is good too, for the same purpose but is a lot more work to apply.
Hi ho....hi ho....it's off to demold, clean, and treat/wax your aluminum & galvanized steel boatlift, you go!
Hey there, not only do you get to pay huge property taxes, but you get to do a lot of work just to MAINTAIN your waterfront property, just to keep it looking nice!