Anybody know something that will remove the lake scum from an outboard engine? Mine is 2 yrs old and looks 20. I've tried everything I know. Some is on the painted metal and some on the black plastic. Kind of white colored. A feller that works at a marina said they use something that is used to clean toilets. I should have inquired further. I'm afraid to put something on real strong that might ruin the cowl or paint. Any suggestions?