2002 Merc 125 WOT stutter (pics and video)

[Levie17]

Not sure where to go from here. Here’s what I’ve done:

re wired dash with rockers

boat lost 7mph at the top.
- cleaned carbs
- added fuel/water separator
- checked fuel
- tried bypassing the rev limiter

Here’s what I found:

2 red and 2 yellow wires from stator to voltage regulator had all melted together. Wires touching. 2 yellows closer to stator also melted together.

Plugs 1 and 2 looked like a nicely toasted marshmallow.

plug 3 was dark black

plug 4 half and half

i tried rotating the coils thinking maybe #3 was bad. No change.

any thoughts? I’ll try to upload a picture or video of the WOT stutter.

 

[Levie17]

[No message]

 

[Levie17]

https://youtu.be/cjSIShQHMJA

 

[flyingscott]

What do rockers in t he dash have to do with anything. Go to cdielectronics.com to get the trouble shooting guide for your ignition. I would do.a.compression and spark.test before anything.

 

[Texasmark]

Assume the yellow power your voltage rectifier/regulator module. Assume the red are power leads for charging the capacitors in the CDI/CDM system. If the melting caused conductors to touch, either like colors or red to yellow, I would "expect" a stator replacement would be in the making. A compression check would tell you if its your reason for the differences in 3 and 4.....you already removed ignition as a potential problem.

You didn't include a new fuel filter in your activities. They are only about 10 bucks and readily available.

3 and 4 get fire and not enough fuel to explode at the lower speeds. This can cause an oily buildup on the plugs. Time for some new plugs....NGK BP8H-N-10 for regular use or if worried about radio interference NGK BPZ8H-N-10 To remedy this problem on my 2002 115, I changed to Iridium plugs (NGK BPR6HIX), gapped out to 0.040" and any time I am running below the kickin of 3 and 4 I tilt the engine up 10-15* to keep fuel from puddling at the rear of the cylinders....an aid to plug fowling.

The tilting of the rear of the engine may seem trivial, but I have run tests, since I just bought this boat used a year ago, and I can have the engine at the trim level I was using at cruising speed, just slowing down where the boat is no linger on plane and watch the engine start to shudder making for a rough idle and low speed.....merely tilting the rear up clears things out, almost instantly, for a smooth idle.

Other thing is punching out of the hole requires time for the fouled plugs to clean up if not tilted up....you can feel the boat misfiring and running solid as it cleans up the plugs until it runs smoothly and rpms are up where they belong. When I apply the tilt up action, I have no clean up process. I punch it out and it goes.

 

[Levie17]

Thank you for the input. I did change the filter. The old one had some sediment in it. Compression on all 4 was 122. I ran it WOT with the timing light on each so I could see the RPM “action”. There was a bit of a miss, but since this boat did not come to me with a tach, I’m stuck guessing for now. I’ll have to have someone with a bit more boat knowledge than I have to check the stator. I did a check all of the other wires though that area and cleaned up some grounds along the way.

Interesting you mentioned the tilting. I have certainly noticed a difference in how the engine runs at different tilt levels.

 

[Texasmark]

Interesting you mentioned the tilting. I have certainly noticed a difference in how the engine runs at different tilt levels.

Years ago...1960-70 general area of time.... Mercury slanted their fishing (20 hp and less) motors. One reason was that OMC was having a problem with their bulging gear case picking up all kinds of debris in areas where one fishes with a small motor...logs, weeds, moss, lilly pads, shallows......having a tilted lower unit with a sleek lower unit was a marketing advantage for slipping over and through such obstructions. BTDT

The other thing they touted was that those small motors were used for hour after hour of trolling and the plugs would foul......one of the combatants was the Capacitor Discharge, fast rise, 40 kv pulse to the plugs. Research and testing told them that if they tilted the power head forward, unburned fuel wouldn't puddle around the plugs and help to foul them.

Well, the 2+2 is a trolling engine design on 2 cylinders...............

How about a DECARB (google the word) and when finished, get a new set of plugs and do the tilt thing at low speeds and then worry about the stator repair.....if you still have issues.

 

[flyingscott]

A factory manual is.a.must for that motor. www.cdielectronics.com should have the trouble shooting guide foe your ignition.

 

[Faztbullet]

It is a ignition problem...not a stator but a coil or switchbox problem..

 

[Levie17]

Thanks. I did read through the CDI trouble shooting. I unplugged the yellows from the voltage regulator, no change. I switched the green/white white/ green, no change. I’ve rotated the coils and the plugs still come back with the same results. I’ll try the decarb and look into the switch box.

 

[Levie17]

I did the decarb today, unfortunately there was no change.

Question:

of the three, voltage regulator, stator, or trigger, what has the biggest impact on the coils?

 

[Faztbullet]

stator, or trigger, what has the biggest impact on the coils?

The connection that ties them together...the switchbox

 

[Levie17]

2002 125 exlpto. Switch box?

 

[Faztbullet]

You have the CDM modules..its either a module or stator. Below is tests

 

[Levie17]

Thank you. I had the stator ohm tested today. Came back within spec. The trigger however was off. I replaced that and went out on the water. No change though. I’ll attempt to tackle to coils tomorrow.