We had a 21' Chapparal bowrider when I was a kid, and the mechanic replaced the exhaust manifold right after we purchased it. About a year later, we opened up the engine compartment and found a mag light shoved under a few hoses. I clicked it on, and it worked! It withstood a trip to Catalina, a ski trip to Havasu and several day trips to Newport, all sitting inside the engine compartment of a 350 MerCruiser. Not bad!