Re: Downside to leaving outboard motor prop in water?
The Kent Ranger 24 that used to be berthed next to my boat had the outboard mounted on a board that could raise it up out of the well. This looked like a stock configuration, perhaps they changed it over the years? It might be worth looking at how other KR24's are configured. There is a sailing club in Renton that brings one up to Goose Bumps races sometimes, perhaps you could check out how they've done it?
Ice in the cooling passages would be extremely bad for the outboard. It's unlikely in WA, but possible since you keep the boat on fresh water.
One of the best things about an outboard on a sailboat is that you can lift the motor out of the water and don't have to deal with the hassles of a folding or feathering inboard prop or the drag of a fixed prop. It is a shame if you can't take advantage of that on your boat. If it were mine I'd try to figure out how to get the motor lifted out of there.
boats that I sail on regularly: Pearson 28-2, Rondar 505, Yankee 30, Blanchard Junior