got a mercury that i pulled the top spark plug and it had some small bits of alumium on it and causing it to not fire this has me very worried. from what i can find out about where the alumium came from it is I think from pre-detonation what ever that is I caught this early and the piston looks to be in good shape and the cyl compression is at 120 lbs. but Im at a loss at what to do next. dont want to take it to a outboard mechanic. without some of you ppls very good advice of what to do next....and has any one had this problem before.