Optimax issues

[Flygaff]

I went out Sat AM with no issues. Just as I arrived back at the marina my port engine stalled. I didn't think anything about it and docked and cleaned the boat. Sunday morning I went down to go out. The port engine was completely dead. No power at all. checked batteries and everything good. After a little digging around I found a blown 20 amp fuse on the engine. I replaced the fuse and tried again. The motor turned over but would not fire. As soon as I let go of the key the fuse blew again. Tried with another fuse, same thing. Engine turned but would not fire. so now I am looking into the key switch itself. I hope this is the issue. it would be the fastest and most cost effective solution. ANY IDEAS?

Thanks

P.S. I caught 15 fluke in three hours - No keepers