Reply To: Mercury force 120 misfiring pics of spark plugs

[Beno]

The original electronics didn’t work at all.. I don’t remember exactly what part was bad. But there was absolutely no spark when I got that block..  They were even a different version of the electronics.

.. From 1989 through 1998 these Mercury Force jet boats went through more different stators. .. CDI boxes…..coils. big crazy capacitor boxes…  its a little insane.

Yep im on the lookout in my warehouse for the resistor plugs .. I’m sure I have quite a few.

I took it on the river for about 20 minutes this afternoon and every so often I would stop and experiment changing the spark advance screw. And quarter turning in each direction the upper and lower carbs..

Shockingly little difference my adjustments made.. I would have thought that would have been big changes.  Nope

Also I pulled the bowl off lower carburetor is absolutely pristine inside.

 

One tricky thing was happening that I still don’t understand is that when I went to take a left or right turn the engine would start to die and misfire ..  now. That engine should have NO IDEA if it’s in a turn of not..  but did not happen just once it happened quite a few times. The moment I started the turn….  I was thinking maybe water in one of the bowls.. but these carbs pick up from the bottom… So that shouldn’t be true.

Any idea?