I have a 1989 Merc 35. Runs great cold but as it warms up at idle seems like it backfires a little and rpm drops way off then slowly comes back. When warm it will often stall out when dropping it in gear and giving it some throttle, makes it a real pain manuvering to the dock or on to trailer. Runs great once its hooked up. Gas is new, plugs are new and I have decarbonized the cylinders. Any insight would be appreciated.<br /><br />Ed