Mariner stalling on idle , will not run under load

[belmont6]

Mariner 55hp 2stroke 2cyl. ( 55EL 663EL-232059) Hello, I have a problem with my outboard engine. Idle is very rough and it stalls. Especially when I go into gear it stalls.Hard to start again if stalled. Engine will run/start at "fast idle". When I put engine under load it cuts out. The problem seems to come from the lower cylinder as when I unplug the upper cylinder with running engine it stalls but when I unplug only the lower cylinder it doesn't stall. Am a complete novice here but it appears both cylinders are properly pressured and both plugs are sparking brightly. Prior to this malfunction I did notice the bulb would harden after a few pumps but will not now. Any ideas?

 

[emoney]

Re: Mariner stalling on idle , will not run under load

This much I know; it only takes Compression, Spark and Fuel to run. If you've done both a compression and a spark test and those are fine it's time to look at the fuel system. When's the last time the fuel lines were examined, etc.? The very first thing I'd check, fuel-wise, would be to make sure the tank is properly venting. I thought I had a problem once that really worried me on the water, until I realized that the tank vent screw had tightened itself down from all the vibration on the water. Once I opened the vent, she ran like a top. Hopefully it's something simple like this for you as well. Good luck.

 

[belmont6]

Re: Mariner stalling on idle , will not run under load

This much I know; it only takes Compression, Spark and Fuel to run. If you've done both a compression and a spark test and those are fine it's time to look at the fuel system. When's the last time the fuel lines were examined, etc.? The very first thing I'd check, fuel-wise, would be to make sure the tank is properly venting. I thought I had a problem once that really worried me on the water, until I realized that the tank vent screw had tightened itself down from all the vibration on the water. Once I opened the vent, she ran like a top. Hopefully it's something simple like this for you as well. Good luck.

Emoney , thanks for the tips. Checked that one too - no joy. I also disconnected the line from the external fuel tank and checked for any leaks with a simple pressure test ( disconnected the line from the engine entry point and clamped end ) - no problems. Getting told that the fuel pump probably needs replacing - does this make sense ?