1999 Mariner 25 h.p - only working on one cylinder

[Inverkelly]

A year ago my 25 hp Mariner failed to go on both cylinders. On the hard using the "earmuffs" it works perfectly. My outboard mechanic over the past year has replaced the plugs, the coils, the power pack (all at considerable expense) but it won't go on both cylinders in the sea, but seems to work perfectly on "the hard". Any suggestions?

 

[racerone]

It does not work " perfectly " on the hard , it just sounds like it because it does not have to do any real work.--It sounds like it is only running on one cylinder. ----So pull each plug wire off while it is running and see what happens.

 

[bilge rat jim]

Start with the basics- ensure that you have good compression on both cylinders, and check for spark using an inline spark tester set at 7/16". If you only have spark on one cylinder switch the ignition coils location and see if the problem follows the coil. If so, replace the coil.
Swap the Brown/White and Brown/Yellow trigger wires. Also swap the Green/Yellow and Green wires. If the problem
moves, replace the ignition pack. If no change, replace the trigger.