3.0 runs rough sometimes ??

[Brandon15]

I have a 99 mercruiser 3.0, runs fine for a while then starts missing and sounds like backfiring, shut it down and sit a few minutes and it will run fine for a few then does it again. Distributor cap and rotor and plugs are all brand new. What should I start checking ?? Also engine temp never gets to hot

 

[Bondo]

What should I start checking ??

Ayuh,..... Welcome Aboard,...... Fuel delivery,..... it's runnin' outa gas,......

 

[Brandon15]

That’s what I was thinking but mine don’t have a actual fuel filter it has some kinda stone like thing in it, do those need to be replaced or could my fuel pump be going bad ??

 

[Scott Danforth]

or your vent on the fuel tank is plugged

or the strainer on the pickup tube is plugged

or the anti-siphon valve is sticking

or there is a leak in the line between the pump and the tank

or there is dirt in the carb and the needle and seat are sticking

 

[Rick Stephens]

A '99 should have a water separator filter on it from the factory. If not I am amazed at the shortchanging of the buyer for the simplest of necessities. If it has a spin on, pull it off and dump the contents into a clear container and see if anything but pure gas is there.

No way from here to tell, but most likely your carburetor got water or crud in it - water and crud always go together unless the water is filtered out immediately. Only way to fix it if it got water in it is to rebuild the carburetor. If I was a betting man, I'd put my money there. But Scott's list is the more complete one in the previous post. Gotta have fuel, several places it can be plugged up.

 

[Brandon15]

Well it’s raining all day today so it will have to wait but thank you all and I will see what I can figure out this week