water inside cylinder yamaha 70 hp

[chompin]

i rebuild a yamaha 70 hp engine and can not
get rid of problem,
water inside cylinder No' 1 the other cylinder are ok i replaced 2 new head gasket.
and still have water on plug .
where can i look for leakage other then head gasket ?

[boats.net]

Check the cylinder head and the inner exhaust plate, they will get holes in them from corrision on the water passage side and corrode through into combustion chamber.