1994 200hp mercury efi

[Mak]

It would run good when I first started it then in 5 min start running bad then I could wait for 15min it would run great all day next day I cranked it on muffs and it ran good for 5 min that started running bad I shut it off and started pulling plugs and they were milky looking worst on bottom cylinder

[Go Time]

milky sounds like some water is getting in the combustion chamber....could be coming in with fuel or leaking in from a crank in block coolant passges, I doubt a head gasket would do this as it would probably inject air into the coolant.

[TEXAS20225]

look at the exhaust divider plate on the back of the motor its the main culprit maybe base gasket but not likely

[Mak]

look at the exhaust divider plate on the back of the motor its the main culprit maybe base gasket but not likely

That's what i thought but had to hear it from someone eles thanks

[Mak]

Well I replace head gasket and exhaust plate gasket and its still doing the same thang I'm guessing power head and exhaust gasket next only thing it runs bad when I first crank it and check the plug there milkey looking not all of them just 3 or 4 I can run it till it gets warmed up and it runs good and the plugs aren't milkey looking