I keep my Tolly engine compartment completely orig, un repainted, and very clean in its 35 years of age. I've got it set up so the salon sole hatches can be opened nearly instantly (or, faster if needed - LOL). Being an early riser... I love to be in there checking-it-all-out and if required servicing everything/anything for an hour or so - - > often starting at around 5 AM when Admiral is still dreaming!
BruceK, many years ago I bought an old wooden Chris Craft. I pulled the engine and used a steam cleaner to clean the bilge. It worked great but it was a full blown industrial steam cleaner that I borrowed from the pile driving company next door.
I used a marine cleaner that was cut with water in a 2:1 mix. Same company that makes POR. It is a spray on and rinse off. Then a plastic putty scraper if desired to lift off the loose and peeling. After that, just paint.