Mercury 75 HP Four stroke Oil in spark plug

[fltony58]

Does anyone know what causes this My mechanic changed all 16 seals and installed a new head gasket. Still had oil in one spark plug ,he can`figure out why
Has anyone had this problem Thanks for your help

 

[dunc333]

has he done a compression test yet it could be seeping through the rings (piston) between the cylinder bore?

 

[fltony58]

He did a compression test it was ok also did a leak down test 3 cylinders were about 7% one cylinder was 15% still has oil in one spark plug