1968 merc 20 hp runs great with muffs in driveway or in a garbage can as well. Trailer it to the lake and launch, everything goes sideways. barely starts,Will not idle. Good compression, spark, rebuilt carb., new fuel lines, fresh fuel. Could this be a timing issue? I tried to adjust carb on lake but could not keep it running long enuff. this outboard does have points. This is my first outboard and im pulling my hair out trying to get some use out it. Thanks