2002 Mercury 75hp WOT Surge

[yzf125]

Hey guys, I have an issue with my 2002 Mercury 75hp elpto. When wide open throttle it just seems to fall flat and surges a bit, If I back off to about 3/4 or 1/2 it seems fine. Runs good out of the hole, I can just mash it and it takes right off with NO hesitation, Its only WOT that I have any issues, It has a feel like its not getting enough fuel at WOT to me, I am just baffled at this point...

Here is what I have done so far to try and resolve this :

1: Removed and cleaned carbs ( checked float height and air screws )
2: Rebuilt fuel pump
3: New fuel filter
4: New Plugs
5: Installed water fuel separator filter
6: New fuel ( Non Ethanol high octane + Startron )

 

[Texasmark]

When at WOT what does the squeeze bulb feel like? If it's anything other than somewhat soft, but full dimensioned and you can feel fuel in it when you squeeze it then your fuel supply is ok. But if it is compressed, or semi compressed and you can't feel any fuel in it your supply either is clogged or the fuel tank vent is obstructed.

On a 2002, like my 90, time to get a new fuel line and Quicksilver squeeze bulb, ensuring you install the bulb with the arrow pointing toward the engine. Upon examination, you will probably find flakes of tan matter clogging the line.

 

[yzf125]

Fuel flow is good and clean.

 

[Texasmark]

Fuel flow is good and clean.

How do you know? What are you using as a metric?

 

[yzf125]

Had my son squeeze the primer bulb at WOT with no change and bulb was as it should be, I guess its more of a rapid on/off hesitation than a surge as it feels like its starving for fuel at WOT is the best way I can describe it.

 

[Texasmark]

Had my son squeeze the primer bulb at WOT with no change and bulb was as it should be, I guess its more of a rapid on/off hesitation than a surge as it feels like its starving for fuel at WOT is the best way I can describe it.

Did you have the surge before you did all this work including the installation of the water separator? If the WS was not part of it, why not bypass it for testing purposes and see if that is your smoking gun. Otherwise how about a crack in a fuel line somewhere in the engine.

 

[yzf125]

I purchased the boat like it is, I just gave it a run without the water separator filter and same thing still, I also did a compression test and all 3 cylinders are 120 psi....

I am starting to think it could be a coil pack breaking down and not a fuel problem now. I noticed anything after half throttle it does it. Is there a way to test the coil packs ??

 

[Texasmark]

I purchased the boat like it is, I just gave it a run without the water separator filter and same thing still, I also did a compression test and all 3 cylinders are 120 psi....

I am starting to think it could be a coil pack breaking down and not a fuel problem now. I noticed anything after half throttle it does it. Is there a way to test the coil packs ??

CDI has a www that has things like that. Others have commented on how well the subject is documented there and have received sufficient information to solve their problems.