1988 75 horse Mariner running rough on long runs

[starkyb]

My 75 horse Mariner will start to run rough after a long run across the river or lake. It starts to slowly lose power and will shut off after I take it out of gear. When I detach the fuel line it will start back up again and run fine. I also noticed when I winterized it it ran smooth as silk and didn't smoke at all when it ran without the fuel line attached. Any ideas what could be going on here.

 

[Faztbullet]

Could be a bad primer bulb......

 

[starkyb]

the bulb is fairly new. It seems that it is getting too much fuel, would a float adjustment be needed. it is oli injected. Is it possible that it is mixing too rich, if so is this correctable?

 

[Texasmark]

Tried a fuel pump kit? What is the condition of the bulb when the engine starts acting up, like squeezed flat or soft to the touch, not hard like when starting but obviously fuel is passing through it kind of thing? Don't think float problems would cause your problems. If they were a problem it wouldn't take a long run to make them act up....opinion.

Heat could be a factor with a clogged cooling system or valve sticking shut but I doubt that would care if you had the hose connected or not.

My 2c,
Mark

 

[starkyb]

The fuel pump was also replaced recently along with fuel lines and plugs and fuel filter. The gas was treated with Seafoam when I filled it up last. Could it be electrical? Maybe just some bad gas. It puzzels me that it runs better without any smoke when the fuel line is detached. I did read something about the enricher may need to be checked if it is running too rich. I have never done this so some tips would be helpful

 

[Texasmark]

I did read something about the enricher may need to be checked if it is running too rich.

The what?

 

[starkyb]

The enricher valve. I've read different things about if it is leaking fuel into the carbs it could cause the motor to run rough.

 

[Texasmark]

Okayeeee. You are talking about the device Merc uses for starting rather than a mechanical butterfly. This is the first time I heard of problems with the enricher.

Easy enough to fix. Remove the input fuel line to it and bend it back sharply and put a tie wrap on it and pull it tight....aka pinch it off. Idea is to remove the fuel from the valve yet keep it from pouring into your engine compartment. Make your normal run and obviously if it still acts up, it's not the valve.

Mark