1997 Mercury 20 hp Carb / Idle Issues

[scumfrogmillionaire]

To all the two-stroke experts:

1997 Mercury 20 hp. Ran great all of last year until I decided to winterize it without stabil and fuel in the tank/carb. I got busy with covid and family stuff. Anyways, took it out of storage and out to the river a month ago. Started up fine, idled fine, ran up and down the river for about 30 mins. Then all of a sudden it would just lose power during WOT until it died. I could idle fine but anytime I would try to throttle up, it would just slowly die. Found that the fuel line had an inner liner collapse. Replaced the fuel line and decided to clean the carb.

While cleaning the carb, noticed that the inlet needle for the bowl float needed replacement. Replaced that and put the carb back on after cleaning. Only way to start it is to open the throttle a little bit while starting. Starts first pull but then the rpm’s surge up and down and sometimes dies. Also shakes quite a bit while running. Idle mixture screw is set at factory specs (1 full turn out from seated) but doesn’t have any effect on the idle since I’m idling at such random rpms. I get spark on both plugs. This has to be a carb issue, right? Maybe I’m better off rebuilding. I did notice the small red seal inside the primer looked pretty deuterated.

Any ideas on which port jet to look for that might be blocked? Thought I cleaned it all pretty well but I guess not.

 

[hotrod53]

I had the issue with loss of power at WOT and it eventually stranded me 6 miles from the truck. Turned out that Stabil turned into a reddish brown snot-like glob in my fuel line.

If your fuel line collapsed, you're suffering from ethanol relates issues. New fuel line, complete carb disassembly, and a rebuild kit would be my approach. At the very least, disassemble and put a tiny wire in every hole in that carb body and squirt it with gumout or brake cleaner...an air compressor is a big help here too. If you have any tags with twist wires on it, they work well for poking the holes. From then forward, use some StarTron in every tankful. StarTron eliminates the effects of ethanol fuel.

 

[scumfrogmillionaire]

Thought I cleaned the carb thoroughly the first time but I just took it apart again and noticed some tiny debris in some of the jets yet. Also, there is a small red seat where the check ball is supposed to sit in the primer assembly that is worn. It doesn’t seal properly. I wonder if this is my issue? Waiting for my rebuild kit to arrive so I can replace it. Keep you posted.

 

[scumfrogmillionaire]

here's a picture. the check ball doesn't create a seal when it's up against this seat. does this mean that fuel is just constantly being fed through the primer jet and into the cylinders?