Mercury 135 weird idle?

colorado08

Recruit
Joined
Oct 19, 2013
Messages
3
I have a 1994 135 Mercury Black max. Good shape motor, i regularly change the fuel filter and change spark plugs twice a year. (at idel) Everytime when i start the motor for the first time after after a day of sitting it starts right up and runs good then after 1 minute of running it acts as if it is going to bog or choke out it runs really rough and the smoke turns a diffrent color. After a minute of that and the motor gets warm it goes back to running like a champ for the rest of the day. Other than that i don't think the motor could run any smoother
 

quicktach

Petty Officer 1st Class
Joined
Aug 24, 2012
Messages
394
Re: Mercury 135 weird idle?

Choke sticking ? Low speed idle adjustment a bit too lean - try 1/8 - 1/4 turn to get more fuel
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,235
Re: Mercury 135 weird idle?

Make sure its trimed up ta level or a touch above after it starts till its good n warm. Might help. Might check tha air temp sensor and/or lines on tha starboard head. Some Merc/Mariner carb motors are JUST finicky so unless your an experienced carb guy ya may never figure it out...............ona computer anyway.
 
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Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
27,036
Re: Mercury 135 weird idle?

Maybe the thermo valve opens a bit before the motor is warmed up? This causes a leaner air fuel mix than the motor is ready for, at that moment? It is likely only a wax controlled valve. After a minute the motor is fully warm and runs properly?

just educated guesses.
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,235
Re: Mercury 135 weird idle?

"thermo or temp sensor valve does this. It acts kinda like a choke. Reads the head temperature. If its low it closes off putting more vacuum thru the idle jets pulling in more fuel (fattens it up). After it warms tha vacume goes away puttin' tha circuit back ta normal (more lean). Check it out after tha motor is warmed up and actin' "normal". Do this by puttin' your finger over tha open port of tha valve for a minute or two. Tha idle should change..........
 
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colorado08

Recruit
Joined
Oct 19, 2013
Messages
3
Re: Mercury 135 weird idle?

Yes it runs excelent right at first start up then starts to run slow and acts as if its gonna bog out for a minute then it goes right back to running great. Im no mechanic should i just take it to a mechanic? or is it not a big deal. it runs great smooth and everything except for the one minute after the first start up
 
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