2005 50 hp Johnson surging

[fish113]

I have a 2005 50 hp Johnson Outboard. After running for 10 minutes or so at high throttle the engine starts to surge and once it starts this it continues to surge violently . I have replaced all of the fuel system and lines from the tank up to and including the fuel tank. I had a mechanic look at this and he replaced the power pack. That did not fix the problem. I also had a mechanic "rebuild" the carburetor. Again . did not fix it. Odd thing is it seems to run fine for about 5 or 10 minutes but then it starts the surging. Any ideas?

 

[sutor623]

Have you check for strong spark on both cylinders once the engine is good and warm?

Have you checked compression on a warm motor?

You say you have replaced the whole fuel system, does this include the fuel pump? Try pumping the primer bulb when the motor is surging. Make sure that your primer lines (coming off the primer solenoid) are all in good shape and attached properly. A simple crack in a primer hose can pull air into that intake mani/cylinder.

Possible that the engine warms up something is expanding and creating an air leak in the engine somewhere. Sometimes when the intake manifold gaskets start to fail (and even reed plate gaskets) it will cause the surging. A good way to test this is to spray carb cleaner around the mating surfaces and see if it affects the idle.

 

[racerone]

Run this motor with a known to be good fuel tank and hose as a test.

 

[175se]

Could the motor be running hot, not sure but could this motor have SLOW.

 

[175se]

WOW, what did this thing just do? Oh well, could the motor be getting hot, I'm not sure but could it be tripping the SLOW if it has that?

 

[175se]

Sorry for the double, my machine had a brain freeze (or was that me lol).

 

[sutor623]

Def. air getting in one way or another. When the carb was pulled did he take a look at the reed valves? How do the plugs look after a long run? Wet or dry