I have a 150hp mercury optimax the under cowl tank fills and the engine runs fine however when moored the oil in this tank drains back to the reserve tank. Why is this and how do I stop it? Is there a check valve if so where?
Thanks for that I had seen the fault finding diagram but thought the brass three way connector at the bottom of the under cowl tank connected to the oil supply line was the check valve. I will now look at the check valve you describe and feed back.
I have taken the check valve out I am able to blow through it one way as I should.
If I try to blow the other way I can just and only just detect some air passing through. I have ordered a new valve an hope this sorts it.
I have blown air through the check valve and re installed. This has solved the problem and everything fine now. I am still waiting for the new check valve and will replace the existing suspect valve when it arrives.
