125HP 2004 Mercury Surging

[michael kennedy]

We have a two stroke 125HP which surges when it gets warm or 10-15 minutes after statring. In rough water it surges in the high range and in flat water it wont deliver fulll rpm. Whilst motor is running if we pump the primer ball it will pick up revs and stop surging. Does anyone have any idea what coulod be wrong.

We have done the following
Plugs
Fuel Filters
Changed all fuel.


Michael Kennedy
Brisbane Australia.

 

[achris]

Re: 125HP 2004 Mercury Surging

Fuel pump diaphragms...

 

[michael kennedy]

Re: 125HP 2004 Mercury Surging

After all the items we changed as follows

[*]Drained fuel tank
[*]Changed all fuel lines
[*]Replaced Filters
[*]Installed larger water seperator fuel filter
[*]Cabrie kits through 4 carbies
[*]Spark Plugs and leads
[*]cleaned out all fuel lines
[*]rebuilt fuel pump
Then we find that it still is surging. We had the boat serviced and a new throttle lever installed at Northside Marine in Brisbane for approx $550 AUD prior to it beginnning to surge. We located another Mercury dealer Coorparoo Marine who diagnosed and repaired the following.

[*]Throttle lever not calibrated correctly when installed by NSM.
[*]Throttle linkages un aligned and now aligned.
[*]Tiing screw cross threaded by NSM, replaced and reset to factory speciifcations.
[*]Spark advance lever not set properly, now reset to manufacturers specs.
total cost including new steering cable $874AUD.
Compression test all 4 cyc at 145psi.

As you can now see if your motor is surging it is usually the result of incompetent tradespeople. Thanks god we found someone who knew what they were doing.