Oil Fill Container Blowing Cap

[waynebellman]

I have a 1993 Yamaha 2 stroke 225 hp that blows the oil cap that is attached to the engine. This cap is located on the right side of the enigine and is used to mix oil into the gas. The engine still runs and I stop refill oil and reseal cap. Obviously, there is something which is creating back pressure to continuously blow the cap. I have had this to a dealer certified yamaha mechanic, and he has replaced the computer and the insert inside the small oil tank in the enigine.
He has also checked the entire electrical system, however, we can not cure the problem. Has anyone encountered this type of problem? Any help would be appreciated. God Bless! I can be reached directly at waynebellman@hotmail.com

[boats.net]

Oil tank may be overfilling, oil level should not be above upper line on engine oil tank.