1998 75hp Force misfire

[TwoFish]

I have a 1998 75 hp Force with has recently developed an intermittent misfire. It happens sometimes just after I start it and last time after cursing at medium speed and slowing to idle speed in the marina. The motor kicks violently (thought I had hit something with the prop) and last time stalled. It started OK after. Does it in neutral and in gear. The first time it happened I found no. 3 plug wire disconnected from the plug. I only realised this because the motor would not get the boat up on the plain. I had run the motor for about 5 minutes at idle before realised there was a problem. I have heard running the CDI units without a ground can damage them.

What I have done so far.

I am most of the way through an annual service.
Replaced fuel lines. (except for the primer bulb)
New plugs.
Cleaned carbie bowl and checked the choke solenoid. Have not disassembled carbie and still need to set idle speed and mixture.
Water separator and inline filters new. No water in filter before changing.

My tacho is reading way too high as well. Not sure if this is related. Charging rate is OK. I intend to run a new wire from the regulator to the tacho.

My plan from here

Set the idle speed and mixture. (Is it worth removing the carbie and cleaning?)

Run the motor at night and mist some water over the electrics to see if I can see any shorts.



Are there any other tests I should be looking at whilst I sorting the above? How can I tell whether a CDI unit is faulty?


Thanks

Cheers

Dean

 

[Jiggz]

Re: 1998 75hp Force misfire

You're most likely have a faulty CDI. The best way to find out is to use a spark tester. And you'll know for sure if it's a CDI.

 

[droach77]

Re: 1998 75hp Force misfire

That motor has a CDM ignition not CDI. You can swap out the 4pin weather pack conns on the modules and move the plug wires in accordance, use either a timing light or tiny tach around the plug wire to see if the problem is moving from cylinder to cylinder. If this sounds confusing go to cdielectronics.com or outboardignitions.com and they have troubleshooting pages for these ignitions for each piece on the motor, they are very helpful. Also make sure your idle screws are set properly, that sounds like a lean backfire. If that does not help you are gonna have to get into carbs for futher inspection and cleaning which is very easy to do on these carbs.




dave

 

[TwoFish]

Re: 1998 75hp Force misfire

Thanks for the replies!

Swapping the wires around makes sense. I will give that a try. I will also check the link to the ignition site.

It does sound more like a backfire than a miss so I?ll give the carbie a clean and reset the idle.


Dean