'98 Mercury 9.9 blowing smoke from telltale

pemmink

Recruit
Joined
Apr 18, 2011
Messages
4
Has anyone ever heard of this?
This motor runs on the bottom cylinder only.
Bottom plug looks normal, top plug looks "very clean".
Both cylinders have spark. Compression is 100, top, 105 bottom.
I quite sure it is smoke and not steam.
From what I can see there is no head gasket, head and cylinder are cast in one piece.
Could this be a cracked top cylinder?
Any ideas would be very much appreciated.
 
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