5.7 mercurser vacuum

[Zinger11]

On the back of my carburetor I have a line that goes to my valve cover. My question is can I plug that line seeing how I don't have anything that requires vacuum? Thanks

 

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[fisherdude]

I believe that is for , if the carb was to flood and gas is going to over fill the carb the gas will get suck into the motor and not spill into the bilge and cause a fire. I would check with a marine mechanic .

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[Bozeman Bob]

To the best of my knowledge the "over fill " line is on the front of the carb and goes back to the fuel pump ,not the valve cover. Why would they have raw fuel possibly being dumped into the valve train ? Most Mercruisers have a hose on each valve cover that goes to the spark arrestor air filter. Any oil-residue that is generated by the engine that ends up in the valves covers is pushed and drawn towards the carb where it gets burnt , in theory with the gas.  Not aware of any vacuum lines that would be attached to a valve cover , if anything there would be pressure not vacuum associated with the valve covers. So if its a 4 banger and only has one valve cover then leave it there. Doesn't hurt to clean the metal "air cleaner ' maybe wash out with old gas or carb cleaner , then wash-soak in a old bucket with dishwashing detergent.  

[Zinger11]

Yes you're right I should have 1 hose from each valve cover going to the spark arrestor which one does and the other one goes to my vacuum line on the back of my carburetor

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[Bozeman Bob]

Have never seen that before, at any rate if it was designed that way I would leave it alone.

[L&M]

What carburetor is on it? It is possible if someone put an automotive Q-Jet on it and utilized the PVC valve & hose, but it is not anything factory. Picture would say a thousand words.

[Zinger11]

What carburetor is on it? It is possible if someone put an automotive Q-Jet on it and utilized the PVC valve & hose, but it is not anything factory. Picture would say a thousand words.

Thank you

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[L&M]

I'll eat crow on that one. Some, but not many with the Mercarb two barrel did have a PVC valve system & that's what is on the end of that hose. No need to plug it , replace the valve if you think there is an issue.

[sherman brown]

• yes that is a pvc line. it should be checked to see if its still working. if it not working right the pvc valve should be replaced.

[Xxx]

My merc has a 2brl carb she flows 500 cfm and yes mine has the pcv valve, eliminating crank case pressure when work hard for long periods of time or for when the old girl gets tired and a rebuild is near or a rering job is needed

[Zinger11]

I'll eat crow on that one. Some, but not many with the Mercarb two barrel did have a PVC valve system & that's what is on the end of that hose. No need to plug it , replace the valve if you think there is an issue.

The thing that was throw me off is my RPMs aren't going that high and it seems to be running a little rich

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[sherman brown]

try replacing the pvc valve. its a cheap try. if the motor has lots of hours on it and burns some oil it probably has some blow by its putting oil through the pvc valve.