2005 Mercury 40hp ELTPO 2 stroke

by Barb
(Kawartha Lakes, Ontario Canada)

2005 40 hp ELPTO 2 stroke mercury runs fine for the first 10 minutes then suddenly starts revving/whailing very high and clunks when shifting gear back down.I bought the boat and motor used so I do not know the history. The previous owner obviously knew the issue but intentionally did not disclose. My marine mechanic has cleaned the carbs and spark plugs, replaced the steering cable, repaired the steering column and looked over everything else on the boat but has not found the problem. He contacted Mercury but all they said is that this problem should not be happening.