2006 Mercury 9.9 gas going into the oil - 3 gallon portable tank

[Prophammer]

Hello , I have a 2006 Mercury 9.9 , my tank looked like the gas cap was cracked from years of use, I couldn't find a replacement cap , so I got a new 3 gallon portable gas tank , now I'm getting gas in the oil , and it locked the engine down , I had to remove spark plugs and get the gas out of the cylinders, to get the engine to crank over. The new gas tank description states it will hold it to 5 psi before venting to atmosphere. My question is this: is 5 psi too much pressure to hold on the carburetor when the engine is shut off ? And the way the gas tank swells up in the summer sun makes me wonder is it higher than that. One other note is the new tank is a different design than my original one from 2006 and I think that is due to emissions. Any help you can offer in much appreciated

 

[roscoe]

Disconnect gas line from motor when not in use. And Crack open the cap to prevent tank swelling and pressure buildup.

Or modify tank by adding a small vent.
There are many ways to do it. See Google or YouTube.

 

[Prophammer]

Thanks for your reply , but I kept wondering, this never happened before and I've own this motor since 2007. So I dug a little deeper looking at my new portable tank. Then Walmart actually gave me the answer I was looking for :

Walmart's "Quicksilver 1200-8M0047598;Tank-Gas-3.3G-12L EPA US Replaces Mercury / Mercruiser. Includes a Diurnal Cap and Mercury's Fuel Demand Valve (FDV), so fuel is provided only as needed by the engine and not forced through under pressure" My fuel line with primer bulb does not have the FDV valve. And this is because my tank came without the hose , from Amazon. I should have got the hose too , my Bad, I hope this info helps someone else before they flood their engine with gas like I did.