02 Merc 125hp 2 stroke timing

[Vernon351]

I'm new to outboards, most of my experience is with I/o ... So I have the factory book for the motor, bit talking to people and looking online I have become confused on how to properly time this motor. I'm looking to set static timing( cranking motor with all plugs removed and in neutral)... My question is do I have to ground out all 4 plug wires or just the number 1 plug? My motor seems to run great put idle is hi, thats why I want to check timing.

 

[racerone]

Timing just does not go out of adjustment on these motors.------Was there a sudden event that made it idle faster ?-----Perhaps adjust throttle idle stop lever to get RPM down.

 

[Vernon351]

I just bought the boat. Just going over the thing top to bottom and realized how high the idle is. I did the idle screws all the way in and then 1 and 1/2 out, starts right up but is idling at 1500 rpm turn them in a bit and start getting lean pop, turn them out to 2 turns idle smooth and goes down to 1200-1300 rpm. Any farther out and it gets rich as hell. Just wanted to double check the timing before I mess around with anything else.

 

[Faztbullet]

On muffs or in a barrel??

 

[Vernon351]

On muffs

 

[racerone]

Hopefully you only adjusted idle screws on the top 2 carburetors.----Do not touch idle adjustment screws on the bottom 2 carburetors.

 

[Chris1956]

I would recommend a Mercury Service Manual. Get an OEM one, as the aftermarket ones are full of serious mistakes.

Unlike an I/O, link and synch between spark advance and carb opening are real important in an outboard.

You will normally set a specific timing when the carbs just start to open. You will also set a specific max spark advance, along with a mechanical throttle stop.

Isle speed is then adjusted by the idle stop screw and throttle control cable.

 

[Vernon351]

You can only adjust idle on the top 2 carbs on this motor as far as I know atleast, it's a 2+2 , no adjustment on the bottom 2.

I have the mercury book, and that's where I'm getting confused on how to set the initial timing. Book say pull all the spark plugs, and attach a spark gap tool into spark plug boot #1 and attach to a ground. Crank motor to set idle timing. Everyone else I talked to and videos i have watched they ground out all 4 spark plug wires . They say it could damage the ignition system if they aren't grounded. So I'm trying to find out what the correct way to do this is . I don't want to mess anything up by doing it wrong, but I've seen several oem and after market books have typos in them.

 

[Chris1956]

I normally remove all but the #1 spark plug, plus the prop. I ground the other plug wires to the block, although not many think the ign system would be damaged, if I didn't. Put timing light on #1 spark plug.

Set the motor throttle to where the carbs are ready to open, but still closed. Now crank motor (jumper starter solenoid) and read timing light. Using the designated screws on the throttle arm, set the idle pickup timing to spec.

Now advance the throttle full and crank the motor and read the max spark advance. Using the designated screws on the throttle arm, set the max spark advance to spec.

OEM service manuals are much more accurate than Utube videos or aftermarket manuals.

 

[Vernon351]

Chris 1956, that's exactly what I did today, and it sounds better and idle is down to 1000-1100 on muffs. Hope to get her in the water Wednesday and see what the in gear idle is and hopefully just some fine tuning. Thanks for the reply!!!