Re: Downside to leaving outboard motor prop in water?
My boat has the same setup. The motor is in a well and it would be a pain to remove if the motor were light, which it's not.
I used Interlux Trilux; the brush-on kind, not the spray-on kind. It's easier to get thick coats on with a brush than it is with the spray. They recommend that you prime with Interlux Primeocon. I don't know if that's completely necessary, but I did use the Primeocon and I never had any adhesion problems. The Trilux helps keep the fuzz (beard) away, but not forever if the boat doesn't get somewhat regular use. Ironically, regular use helps keep growth off the outdrive, but it makes the paint on the prop wear off more quickly.
Make sure when you paint, you don't block any of the exhaust blow out holes or the intake. On mine, the intake has a fine screen and since the screen couldn't be painted, it still grew some fuzz from time to time. It usually came off easily by jumping in with a toothbrush and giving it a scrub a dub dub.