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Author Topic:   Carb adjustment
wetdogsoup posted 02-22-2004 09:55 PM ET (US)   Profile for wetdogsoup   Send Email to wetdogsoup  
With service manual in hand, have tried to adjust idle mixture screw for a '99 merc 60/2.

Initially opened screws to rec. 1 1/8 turns. Manual says to close screw CW until engine bogs, then open at least 1/4 turn. It never seems to really bog down when I start to close one down - Are you supposed to adjust just one carb at a time or all 3 (3 cyl engine) together?

From the way she's running, can you tell if your setting is too rich or too lean? The manual says "check for too lean a setting on acceleration". What the heck does that mean..... will she stall out on acceleration if too lean?

I also have problem of hesitation/bogging (1 sec) when I go from idle to WOT.

I've sprayed a can of gumout carb cleaner and also let the engine sit flooded with same for 15min. I've run 30 gal of fuel with twice the rec amount of Techron mixture to help clean out carbs. (prior owner let boat sit up for months at a time w/o any storage prep).

Next I'll try taking apart carbs and cleaning unless anyone has other suggestions.

thanks, don

Clark Roberts posted 02-23-2004 08:08 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Wetdog, if you made adjustments with boat on hose and in neutral that may account for the problem. Idle/air needle valves need to be adjusted with boat in water, tied to dock, engine warmed up and in fwd gear. The propeller load and the backpressure of water column in mid section are essential to proper adjustment. Follow the drill in the manual and BTW, turning CW leans the mixture (less gas and throttle air is constant/unadjustable) and CCW richens mixture. These adjustments only effect idle and speeds up to about 1600rpm at which point the high speed (fixed) jet takes over. Adjust idle to approx 700 via the timing/throttle arm screw (engine idles on timing only) and make sure that the throttle actuating linkages are adjusted properly per manual. The roller on the throttle linkage should NOT touch the cam actuator with engine in neutral and if it does you cannot ever get a consistant idle. Happy Whalin'... Clark... Spruce Creek Navy
wetdogsoup posted 02-23-2004 11:55 AM ET (US)     Profile for wetdogsoup  Send Email to wetdogsoup     
Thanks Clark,

this morning the search func is working again and I was able shed more light on my condition. I see now that:

1 idle screw adjustment is not minute, but rather 2 - 4 turns from too rich to too lean

2 use higher ratio of techron ( 1 bottle to 6 gal gas)

3 engine will hesitate on WOT acceleration if mixture too lean

4 check plugs for clues on mixture setting

As per your note, she was tied up at the dock and in idle forward while adjusting. When you say "The roller on the throttle linkage should NOT touch the cam actuator with engine in neutral", is this what the manual refers to as ".005 - .04 inch gap between roller of cam follower and throttle cam".

Thanks again Clark


Bigshot posted 02-23-2004 02:15 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Do not adjust while on techron mixture. Techron will make it run poorly. If she does not clean out from Techron, have carbs cleaned.
Clark Roberts posted 02-23-2004 03:27 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Wet, yes that's the same roller!
wetdogsoup posted 02-23-2004 07:03 PM ET (US)     Profile for wetdogsoup  Send Email to wetdogsoup     
Thanks guys!

Using gas w/o excess techron and turning the idle mixture screws very slowly while adjusting did the trick.

Heck, she's even running well enough now that I'm going to postpone that carb rebuild!!


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