86 Merc 25 xd Igintion problem?

[acwd]

ok heres the deal. It randomly hits on one cylinder. Might hit on that cylinder and run on it for awhile then quit. and do it all over again. So heres what I have done. They had put new plugs in and you could tell that the one wasnt firing. it was like new and wet. Tried different plugs same thing. Switched the wires from one coil to the other to check the coils. The problem went to the other coil so the coil is good ( jumps a 1 inch gap). Checked the stator and trigger out put. Cranking it over got 120v going to the switch box (thats with a fully charged battery and plugs in it). I am betting on the switch box. Anyway to check it? The guy claims that they changed the coils and switch box and it still did it. Anybody have any other ideas?

Thanks
Steve

 

[cincinnati]

Had a similar problem on my '88 25 HP Merc & it was the switchbox.

Sometimes it was fine, sometimes it would start on one cylinder & then begin hitting on the 2nd after the motor got hot. Very random.

The last time I suffered w/it, the motor wouldn't start @ all, so we fished around the ramp on the trolling motor. The day got stinking hot &, just for stupidity sake, I cranked the Merc & it started & ran fine. (Remember, when you're testing electrical components, the values change w/temperature!)

Finally bit the bullet & bought the switchbox. No trouble since.

 

[JMichael]

So you're saying someone else has attempted to fix this issue and in the course of their work, they replaced the switchbox and the problems remained the same? Have you checked all the associated wiring that doesn't get replaced when the new parts are installed?

 

[yareelohim]

Had the same problem on mine. One of the green/white wires (+) from the switchbox to the coil was bad. Got a new switchbox and both cylinders started firing again

 

[Charger25]

" Switched the wires from one coil to the other to check the coils."
If your saying that you switched plug wires , Might want to try and ohm them out .