Misfire 1998 90 hp force

[bmurr01]

hi I'm new here but your forums have been really helpful. I have a 1998 90 hp Force 3 cylinder 2 stroke. Went out on lake first time this summer and ran great. Had a buyer and went next day let him run the boat and wouldn't idol and started misfiring badly. Did manage to get it running WOT but about 5200 rpm. When we would slow down it would start acting up again. I was able to keep idol but I would have to tap the choke to do so. Cleaned carbs, new filter and new gas helped the idol but still misfiring at idol and anytime I tried to hold at steady rpm's. will rev in neutral just fine. Found that the #2 pack was not firing and causing the motor to sputter and spit till it dies. (Pardon my ignorance but is that called detonation when the fuel in the cylinder isn't able fire?) The tachometer is reading just fine. First thought coil pack but if I switch connectors from other coil pack the #2 fires just fine. This engine has a voltage regulator on it so not sure it that would cause a firing issue. just to be safe I bypassed the regulator and disconnected the yellow wires from the stator. If the problem moves when I switch connectors on the coil packs does that mean its a stator or trigger problem? I don't have a dva box just a regular multimeter. Any help would be appreciated. Guy still wants to buy boat but not for much longer if I can't figure this out. Thnx

 

[pnwboat]

One of the other CDM modules (coil packs) that is bad can cause a good one to misfire. Connect all of the 4 pin modular connectors to the 3 CDM modules as normal. Disconnect the other 4 pin modular connectors one at a time and crank the motor over like you're trying to start it. Do #1 cylinder first. If spark is restored to #2 plug, then #1 CDM is bad. If no difference, reconnect #1 cylinder and pull the 4 pin modular plug for #3 CDM. If spark is restored to #2, then #3 CDM is bad.

If disconnecting the 4 pin to either #1 or #3 CDM has no affect on spark for #2 then the next thing would be to check the stator resistance and magnets on the inner circumference of the flywheel.

Look up underneath the flywheel. You should see six magnets glued on. Make sure they are in place and not cracked or missing.

Disconnect the White/Green and Green/White stator wires at the bullet connectors. Read the resistance between these two wires where they come out from under the flywheel. You should read between 500 - 700 OHMs.

 

[bmurr01]

Thnx for the fast responce. I understand exactly what you're asking me to check and I will tomorrow. I forgot to mention that the stator looked brand new and I think it was replaced last summer. I did check the resistance and it measured 690 OHMs. I can't see the magnets due to the way the stator is made. Has some type of cover around it. Will be Monday before I can get a puller to take flywheel off. The trigger doesn't look like it's been replaced. If the coil packs all seem to be fine what could the culprit be? Can the trigger cause the problems i'm having?

 

[pnwboat]

It's possible, however the trigger used a solid state Hall Effect sensor, so you cannot use resistance to check it. You need a multi-meter with a "Diode" checking function.

Just so you know what to look for, here is a picture of the underside of your flywheel with the six magnets. The stator sits in the area between the magnets and the center hole. For the 1995/1996 and later flywheels, there is a special puller designed to engage the threads inside the raised lip that goes around the hole in the middle of the flywheel.

 

[jerryjerry05]

IF?? the magnets or magnet came loose you'd see pieces of it and the stator laying on the top of the motor.
​Detonation is when it fires. Not misfires.

When you switched wires and got fire on #2 did the other coil fire with the leads hooked up?

If it fires when you move things around it's probably not the trigger.
Check all the connections for black or burnt spots in the wiring loom.

Do a compression test?

Unhook the tach and see if that makes a difference?

outboardignitiondotcom has test procedures for the motor.

Oh yea Welcome.

Make it easy on the people who read the posts by breaking the paragraph down. One long sentence is hard to read and follow.

 

[bmurr01]

Ok guys, Wasn't able to work on motor yesterday. I had the pleasure of moving my sis-n-law all day! Fun fun for me.

I double checked the stator and looks like new. the magnets on the flywheel all look intact and no visible marks of anything hitting or rubbing. also checked the resistance on the stator and still 690 ohm's.

If I unplug the connector to #1 coil pack there's still no fire on #2. Same thing when I unplug #3. If I switch the #1 and #2 Connectors then #2 will fire but not #1 so makes me think its not a coil pack.

The stator has a green/white stripe wire that runs to both the #2 and #3 coil packs and a white/green stripe wire that runs only to pack #1. If #3 is still firing does that mean the green/white stripe stator wire is working properly?

The trigger has a separate wire for each individual coil pack. That's making me think that maybe it's the trigger. What do you guys think?

 

[jerryjerry05]

Doesn't sound like a coil.
​Try swapping the trigger leads?

 

[pnwboat]

It sure seems like a possible trigger issue. Take a really close look at the trigger wires themselves. Make sure you don't have a bad trigger connection, or a damaged trigger wire for number 2 cylinder. Unplug the connection for number two cylinder and clean it up then reconnect it.

 

[bmurr01]

jerryjerry05 thanks for that advice. Didn't think of that. I switched the #1 and #2 leads out of the trigger to the bullet connectors and the #1 quit firing and the #2 started firing so definately think that's the source of the problem.

pnwboat I checked the continuity between the bullet connector and the 4 pin connector. Tested fine but of course that can easily give a false reading.

I would like to check the wires from right out of the trigger to the bullet connectors but I'll have to get the flywheel off to reach them. They are really old looking and are really flexible so they could have some breaks in them.

Gonna order a new trigger today as I believe that is the problem. I'll post soon as I get it installed and tested.

Where's the best place to order? outboardignition.com?

 

[jerryjerry05]

OI sells it for About $53
You might get it cheaper on E-bay?

 

[bmurr01]

Hey Guys, Thanks for all your help.

Turns out the source of the problem was in fact the trigger. I ordered it from Outboard Ignition for 63 dollars plus shipping so not to pricey.

The trigger that was on the motor was not color coded like the factory so might have been a cheap-o. Anyway plugged the new one in, checked the flywheel and magnets for any damage, then reinstalled everything back and it fired right up.

Hopefully this thread along with the great advice you guys have given can help someone else!

Everyone has told me that the trigger very rarely goes bad so eliminate all you can and be sure that's what it is.

Thanks again guys for all your help!!

 

[pnwboat]

Glad you got it going without having to spend too much time any money.