Amount of growth/zebras can depend on the current. My father keeps his boat in a marina with very little current, and hey gets a zebras, and a decent amount of growth (unpainted bottom). This is also in Lake Ere if it makes a difference. At the end of the year he cleans with muriatic acid (get it at a pool store.....MUCH cheaper. Wear mask/gear as it's some nasty stuff). I keep mine at the Oak where there is some current. Painted bottom, growth is very minimal, and some zebras collect on trim tabs, but nothing too bad. Unfortunately, can't speak on any outboard info, but always see them up and out of the water.