Re: painting an outboard
That will work like a champ. However try something a little more " friendly" first. Some of the citrus based cleaners will do wonders. As far as the wire brush is concerned don't get overly aggresive with it or you'll find yourself with some gouges from it. Try a green 3M pad soaked with the cleaner.
Soak everything really good first and let it sit for an hour or so. Wash off with a high pressure hose or better yet a pressure washer. What's left then do the green pad scrubby thing. Finish off cleaning with the smallest amounts of thinner ( whatever the paint calls for) that you can manage.
Or just trailer it to a car wash and start from there. Most of them have a degrease cycle so it just might save you a buck or two.
You will still need to properly prep it all before you paint.