My 2005 merc 90 2-stroke runs pretty rough at idle while in gear. I can run it wide open all day with no issues but once I come back down to an idle, it starts stumbling a little and just doesn't sound right.
Does this sound like a carb problem?
Are there any ways/things I can do to clean them?
To my knowledge, the motor has probably never had the carbs serviced. I've changed the plugs but haven't messed with anything else.
Definitely sounds like a carb problem. Probably a good time to consider going through them completely (including kits, and complete disassembly/cleaning).
No "miracle cure in a bottle" for this, BTW.
That being said... you might try opening the Idle Air Mixture Screws (one on each carb) precisely 1/4 turn COUNTERCLOCKWISE. See if that doesn't improve the situation.
The burn rate (and butane rating) of today's fuels is quite different from what we had when your engine was designed (and it has no means to compensate on it's own).
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
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Thank you for the quick response and help! I decided to tear apart the carbs and rebuild them myself. I'll have them rebuilt by this weekend and I'll repost with the results. I'm also going to change fuel filter and plugs to.
I'll adjust the carbs to once I get them put back on. That makes sense with the burn rate (never woulda considered it)
I also am going to run ethanol free gas through the engine from now on. I'm lucky enough to have a couple local stations that offer it still!!!!
Modified by fishman400 at 11:54 AM 3/14/2012
well got the carbs put back together. (they looked perfect when i took them apart) i made sure to clean out all passages and re-intall with new gaskets. took out to lake sunday and prob was still there!?!?!
then i noticed i had the wrong plugs on the boat. i was given buhw-2 and the motor calls for buzhw-2s. i didnt think this could/would make a difference, but installed old plugs i had (that were correct) and motor def seems to run better. havent got to put her in water yet, but so far, she really seems to like to right plugs.
further research says those plugs can actually make a difference. this would also make sense cause the problem goes away at WOT and runs perfect, it's only in gear while idling when it doenst run right. i'll take her out tomorrow and let you know i find.
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