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1981 Mercury 115

M

Merc79

New member
Hi, I'm replacing #3 piston in my 1981 Mercury 115 2 stroke because the top started to melt. There's no real indication what caused the damage to the piston, all other pistons are in excellent condition and no damage to cylinder walls. Could there have been a carbon deposit got hot? Or could water have been drawn into the one cylinder? I purchased a complete gasket kit for the motor when I bought the piston and I was wondering how important is it to replace the exhaust cover gasket? I have not taken the cover apart yet, I'm sure the bolts have to be heated to be removed.
 

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That pre-ignition damage and from a bad trigger. Yes cover needs removed to clean molten transfer from inner exhaust plate as it can break loose and sucked back into cylinder from exhaust pulse
 
Thanks for the reply. I'm new to outboard motor repair. And a bad trigger as in an issue with the ignition system possibly?
 
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