1978 4hp Mercury wont stay running

[bowhunter2]

I have mercury that will not stay running. After approximately 5 minutes the motor will shut off by itself. It does not mater if it is at idle, part or wide open throttle. After it dies I can partially choke the motor and it will start back up. I have cleaned the fuel tank, checked the fuel filter and flushed the lines. <br /><br />Any suggestions will be appreciated.

 

[Laddies]

Re: 1978 4hp Mercury wont stay running

Is the gas tank vent working and how about a fuel pump kit

 

[bowhunter2]

Re: 1978 4hp Mercury wont stay running

The motor uses an internal gravity fed tank. The motor will die with the gas cap off so I know that ventilation is not an issue. I can pull the fuel line off of the carburetor and gas flows freely. <br /><br />Thanks, bowhunter2

 

[andrewkafp]

Re: 1978 4hp Mercury wont stay running

Have you checked the fuel pump diaphram ?

 

[Paul Moir]

Re: 1978 4hp Mercury wont stay running

There is no fuel pump on that engine. At least I think there isn't: this is the 2 cylinder one right?<br /><br />If so, on the starboard side of the block near the bottom is a little fitting that hooks up to a tube that runs to the manifold. That fitting is supposed to be a check valve. If it isn't working - it should only let air through one way; out toward the manifold - then the engine can load up and die in about five minutes. If it's plugged it may just need to be cleaned.<br /><br />I've got to say, getting a 2 cylinder Gnat to idle right is a challenge!

 

[bowhunter2]

Re: 1978 4hp Mercury wont stay running

Thanks Captian, Your right the little moter is a 2 cyinder and does not have a fule pump. I will check the fitting and one way valve.<br /><br />Respectfully, bowhunter2

 

[bowhunter2]

Re: 1978 4hp Mercury wont stay running

I pulled the fitting off and the check valve is is open both ways. I will try to find a replacement. <br /><br />Thanks again.

 

[Paul Moir]

Re: 1978 4hp Mercury wont stay running

Replacement is still availabe from the dealer! I got mine for around $10 locally. Hopefully, that'll solve the problem.<br />I fixed up one of these for my brother and in the process ended up got to know it pretty well. I've got some notes on it in a text document: timing specs, spark plug info, that sort of thing. They don't take the place of a manual but they might be helpful to you.<br />If you want em, fire me an email at paul.moir@ns.sympatico.ca

 

[bowhunter2]

Re: 1978 4hp Mercury wont stay running

Update - Replaced the check valve and it purrs like a kitten. Thanks for your help. <br /><br />Going fishing tomorrow!!!!