2000, 50hp, 2-stroke coughing between 1400-2600 rpms

[somersetlaker]

I recently purchased a pontoon with a 2000, 50-hp, 2-stroke Mercury outboard, oil-injected. (200 hours).

The engine at random times will sputter and cough between 1400 and 2600 rpms. Below 1400 or above 2600, it seems to run fine.

This isn't always a problem. It could happen shortly after shoving off ... or not ... or it can happen after 30 minutes of cruising. The coughing will happen about every 5 seconds at its worse.

 

[Toddboat]

Re: 2000, 50hp, 2-stroke coughing between 1400-2600 rpms

I recently purchased a pontoon with a 2000, 50-hp, 2-stroke Mercury outboard, oil-injected. (200 hours).

The engine at random times will sputter and cough between 1400 and 2600 rpms. Below 1400 or above 2600, it seems to run fine.

This isn't always a problem. It could happen shortly after shoving off ... or not ... or it can happen after 30 minutes of cruising. The coughing will happen about every 5 seconds at its worse.

Coughing is fuel related. If hesitation, surging, coughing, etc, happen at a certain RPM range and not others, it points towards a carb problem because carbs have three circuits for different RPM's... idle circuit, low speed circuit and high speed circuit. Sounds like the low speed circuit on one or more of your carbs is blocked up. Read the many posts on this forum on how to clean the carbs. Preferably you can locate exactly how the fuel flows through the low speed (intermediate) circuit and target that part of the carb with spray cleaner. Soaking the carbs is a good approach to thorough cleaning. The gunk in the carbs is from bad fuel or ethanol eating away at the fuel pump membrane or fuel lines. Replace membrane and fuel lines as required. To minimize future occurance, add fuel stabilizer at each fill up, and especially before periods of storage.
You can try first running seafoam through the motor a few times. If it doesn't get rid of the coughing, then clean the carbs. If it's only minimal gunk in the carbs, seafoam can sometimes do the trick.

 

[Texasmark]

Re: 2000, 50hp, 2-stroke coughing between 1400-2600 rpms

+1. That's about the time that you are taking over from low to high speed jets. Probably crud in the high speed jets. I use Sea Foam in every tank and it has proven itself to me. However, I had a problem that turned out to be carb related and it was a piece of hose clogging the high speed jet on one of my carbs....'02 90 hp. SF wouldn't have been able to fix that. But upon opening the carbs, there was absolutely no sign of any varnish or fuel related crud.....and that's after 10 years of operation with carbs never touched....thanks, SF.

HTH,
Mark