Sport Jet 120 with no fire on bottom 2 cylinders

[caseman]

I bought a 1995 Rinker with a Sport Jet 120. I have good fire on #1 and #2 cylinders but no fire on #3 and #4. It has the red stator and I have disconnected the rev limiter. I have been told this is a force engine. What would cause the it to lose power on only two cylinders or how do I test it. I have 30 years experance as a mechanic on construction equipment but marine engines are new to me.

 

[pnwboat]

Re: Sport Jet 120 with no fire on bottom 2 cylinders

There are several types of ignition systems used. The Prestolite ignition uses baby blue coils and baby blue CD packs. The Thunderbolt ignition has dark blue coils, almost look black, and a switch box. Which one do you have?

 

[caseman]

Re: Sport Jet 120 with no fire on bottom 2 cylinders

It all looks black. The all 4 coils are made together. I will check tonight to see there are any names or numbers on them.

 

[pnwboat]

Re: Sport Jet 120 with no fire on bottom 2 cylinders

Sounds like that is the Thunderbolt ignition. There is a plastic cover that goes over all four coils that makes it look like they are one unit. Check all of your ground connections. Can't remember off the top of my head but I believe each coil has a ground wire. You can try swapping coils around to see if the problem moves. If it does, it's probably a bad coil(s).