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1998 Mercury 20hp 2-stroke, runs great idle cuts out att full throttle

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Bobbechk

New member
Hello

I've been having some problems with my grandfathers old 1998 Mercury 20E 2-stroke, It starts very easy and runs great at idle and low speed but when I push the throttle it will start acting up and cutting out, but strangely I have gotten it to run well full throttle a couple of times for extended sessions after restarts...
At a certain throttle it will become almost like a pendulum, going up in rpm then cutting out and falling down then up again repeating.

The problems started when I started it up a couple weeks back, it was running very bad (kind of the same problem but it cut out right away) and when I opened it up I found the "idle-wire" completely loose inside, I reattached it but I'm not completely sure it's correct since I can't find any instructions (I connected it by twisting it inside a rectangular hole on the arm connecting to the control lever) anyhow it seems right but the idle-wire is kind of loose.

I also went over the fuel line and changed the bladder etc. but everything there seems fine (it does not react to pumping the bladder when acting up)

Here's a video of it running: https://youtu.be/VciXR2RL61A?list=UUzBwqB1NIf6xZzmEW_QVydA

Last year I also had a guy clean the carburetor with ultrasound and used a kit to replace what needed replacing along with fuel filter etc. and It ran great after that.
(It does not run any better with the choke out but rather cuts out as expected.)

So I'm not sure what to do, My limited experience tells me I would have to go trough the carburetor again but I wanted to see if someone has any better suggestions...?
 
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Mine would run real rough at idle and eventually cut out. The rpm's would be all over the place. I rebuilt the carb last night, and that resolved it. The seat in the primer was coming apart, so the small check ball couldn't seal properly. Hopefully this resolves your issue as well. Make sure to blow out all of the jets with compressed air as well.
 
scumfrog_millionaire said:
Mine would run real rough at idle and eventually cut out. The rpm's would be all over the place. I rebuilt the carb last night, and that resolved it. The seat in the primer was coming apart, so the small check ball couldn't seal properly. Hopefully this resolves your issue as well. Make sure to blow out all of the jets with compressed air as well.
Click to expand...

I replaced the internal fuel-lines and clamps and it seems to have solved all the issues!

I've only run it for like 30min and I've had some "luck" in the past were it would run great until next time so I'm not 100% yet but it seems reasonable that the original fuel clams were the culprit in my case...
 
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