Merc 2000 125HP 4 cylinder running weird

[gobucs1]

My neighbor came to me to post this since he is not the greatest with computers.

He has a 2000 125 4 cylinder model that shuts off 2 cylinders when running at low speeds. He said he was coming in and the motor started running bad then died. He was able to restart it at high rpms but the motor was running rough and he eventaully got towed in.

I pulled his carbs and they looked great, I cleaned them anyways. Some of the fuel was drained and it looked weird like the gas had turned to crap from the ethanol.

Is this an ethanol problem? Motor was last ran a few months before this last time but the motor did run fine all day before having this issue on the way back to port.

Any ideas? Thanks!

 

[CharlieB]

Re: Merc 2000 125HP 4 cylinder running weird

The 115/125 4 cyl Merc/Mariner is a 2 + 2 system where only the top 2 cyl /carbs have idle circuits and fire, the bottom 2 cyl/carbs do not pass enough fuel to support combustion until the throttle plates are opened and air flow/engine speed increases above an idle, there is an accelerator pump plumbed to the bottom 2 cyl's that gives a small squirt of fuel to assist the bottom cyls to fire while the throttle is being opened.

A contaminated fuel system is the most probable culprit for your neighbors problems. Clean the carbs, install a water separating filter to prevent a re-occurance.

Once the 2 + 2 system is adjusted per the factory manual procedures most people will not notice anything out of the ordinary and don't even realize that it is a 2 + 2.

 

[gobucs1]

Re: Merc 2000 125HP 4 cylinder running weird

CharlieB Thanks! Seems like a neat system on that motor.

I am going to help him empty all the old fuel out tomorrow and to install a fuel water seperator.

Then we will add ethanol free gas and hope for the best.

 

[CharlieB]

Re: Merc 2000 125HP 4 cylinder running weird

Do you have access to the FACTORY Service Manual?

Synching the carb linkages and adjusting the throttle pick-up roller to the timing control is critical as well as setting the gap on the accelerator pump to the throttle cam at WOT.

I have a well made .pdf copy of the manual, courtesy of another member, that I can send you, send me a PM with your email address.

 

[gobucs1]

Re: Merc 2000 125HP 4 cylinder running weird

I sent you a PM and if none of those adjustments have been messed with do they need to be adjusted or just looked at? He had to work late so we didn't do anything on it today but tomorrow/this weekend for sure.

Thanks!

 

[I'D RATHER B FISHN]

Re: Merc 2000 125HP 4 cylinder running weird

Is this 2+2 system the same for a 2004 125hp 4 cylinder?

Thanks,
Mike

 

[CharlieB]

Re: Merc 2000 125HP 4 cylinder running weird

As far as I know, nothing has changed but the price.

 

[I'D RATHER B FISHN]

Re: Merc 2000 125HP 4 cylinder running weird

Thanks