Oil getting in gas tank

[Dstran]

Hello

I've got a 1996 2.0 L Mariner.

Boat runs great but when it sits for any length of time oil backs down the gas line into the tank. Sometimes it will do it after 5 minutes sometimes it will be fine all day. It drained the oil tank reservoir this winter into the fuel tank. The oil reservoir pressures up so much it actually bulges, is this normal ?
The boat started doing this last yr and I had it in and looked at but they weren't able to figure out what was wrong.

Anybody have any ideas ??

 

[timebandit]

The pulse limiter valve is where I would start. The valve is on the stbd side if the block. Follow the air hose into the motor.

 

[Dstran]

I'm guessing then it's not normal for the oil res to be pressuring up or staying pressured up after the boats been turned off ?

 

[Dstran]

The oil check valve was also changed last year and didn't solve the problem.