2008 Mercury 50hp 2 stroke low hours

[joejas]

I have a 2008 Mercury 50hp 2 stroke that was bought new as part of a boat package. I have always noticed a rough idle but was told that is common to 3 cylinder 2 strokes. Here is some of my observations that were done on the lake after engine was warm. Idle is rough but when I hit the choke/enrichment valve for only a 1/2 second the engine will smooth out for 10 seconds or so. Rough idle then hit choke/enrichment valve for 1/2 sec and gets smooth again for 10 sec. If left to idle rough she sometimes stalls after sputter and vibrating. Low speed at idle and just beyond is rough but the choke for 1/2 sec. smooths it out and the engine perks up and idles fine. Trolling speed it out of the question because after 30 seconds engine gets rough, shakes/vibrates and somtimes dies. Mid and high speed is smooth and without issues. It just seems idle and low speed are rough and sputtery but once I increase throttle past about 1/4 throttle it acts like a different motor. Makes for tough and dangerous manuvering around the docks and busy ramps. Less than 20 hrs on motor.
I drained the fuel tank and checked the screen then refilled with fresh fuel and stabil(as always) but still the same.

 

[Texasmark]

Re: 2008 Mercury 50hp 2 stroke low hours

Well, being a loop charged 3 cyl engine with 3 carbs, since you use fuel additive and all (would prefer Sea Foam to Stabil personally for 2 cycles) all your fuel processing parts should be clean. I'd say that your running lean on at least one carb. Might dig around the archives about articles on setting up the carbs on 3 carb'd Mercs. I have the 90 3 cyl Merc and yes it idles rougher than a 4 cyl or 6 cyl tower of power, but not all that bad. I notice it most with my current SS 24P prop. If I drop down to a lighter 21P prop or lower it is hardly noticeable.

The high speed jets are fixed and your remarks about performance when operating from them suggest to me that the engine is in fine shape. Just need to get the "adjustable" low speed jet(s) tweaked.

Mark