Sport Jet 90 has no spark at bottom cylinder

ragnar333

Cadet
Joined
Jul 15, 2013
Messages
25
I'm just about at my wit's end with this thing. I recently bought a 93 SeaRayder with a Sport Jet 90 engine for cheap money (I know, I know,lol). The guy that I bought it from said that it ran great when he parked it at the end of last season. He said that when he launched it this season, that it didn't seem to have as much power as the last time he used it. He never got it checked out and decided to sell it.

When I got it home I started checking things out and soon discovered that there was no spark at the plug on the bottom cylinder. I did some reading and researching and started to troubleshoot it on my own. first I checked if the coil was the problem by swapping out the lower coil with a known good one. Still no spark. Next I figured that the issue was either with the switchbox or trigger. I called a local Merc dealer to check on parts availability and discussed my problem with him. He was certain that the problem was with the switchbox because only 1 cylinder was not firing. He said that it was possible that the trigger could be causing it, but it was rare and he seemed sure that the switchbox would fix it.

Well, I ordered and installed the new switchbox and there is still no spark at the bottom cylinder. I assume that the stator is good because I have good spark at the other 2 cylinders, and during inspection I found a tag on the stator leads that showed that the stator had been replaced with a CDI stator in 2004. I have very thoroughly checked all wires and connections, and the only thing that I noticed out of place is that there are a couple of small pieces missing from 2 of the glued on magnets under the flywheel. That shouldn't affect spark on one cylinder, should it?

So... is it safe to assume that a new trigger will fix the problem? Thanks in advance for any and all input. I'm about ready to pour gas all over this thing and light it.
 

Bosunsmate

Admiral
Joined
Apr 7, 2012
Messages
6,135
Re: Sport Jet 90 has no spark at bottom cylinder

Where are the damaged magnets, inner or outer hub of flywheel?
 
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quicktach

Petty Officer 1st Class
Joined
Aug 24, 2012
Messages
394
Re: Sport Jet 90 has no spark at bottom cylinder

Checked the lower spark plug wire itself ? Checked wiring from switchbox to the lower coil ? All grounds clean and good ?
 

oldman570

Lieutenant Commander
Joined
Mar 25, 2011
Messages
1,615
Re: Sport Jet 90 has no spark at bottom cylinder

The CDI web site will tell how to test the stator or trigger, and Boatinfo - The library, containing manuals, brochures and other technical documents from the last hundred years! should also, if you do not have a manual for the motor. You will need to move the slider button under the manuals to get to the one for your motor. The trigger wire for that cylinder could have gotten rubbed by the flywheel and can be the cause of the trouble. Test everything before buying any electrical parts as most dealers will not take them back , and some are not cheap. JMO
Oldman570
 
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ragnar333

Cadet
Joined
Jul 15, 2013
Messages
25
Re: Sport Jet 90 has no spark at bottom cylinder

Thanks for the replies. I have an update on it. I ordered and installed a new trigger and now it runs perfect. Although I did end up buying a switchbox that I didn't need (as advised by a Merc "expert"), I learned a lot about what makes one of these things tick. I have read other similar Sport Jet threads on here and I learned a very important lesson.

If you are going to own and operate one of these cool little boats with the Sport Jet 90, you absolutely need to own a DVA meter and learn how to test all of the electrical components in the ignition system. Had I actually tested the trigger, I would have saved a lot of time and money.
 
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