1995 force 40 no spark

[Dwharris09]

Im new to this forum, and any help would be greatly appreciated. I recently brought my dads old spectrum dominator out of retirement. It has a Force 40 by mercury marine engine. She has beem sitting for around 12 years and i got tired of seeing her sit there. I put fresh battries in (thankfully my dad took them out when he stored her) took the carb off and clean it out along with the whole fuel system (fuel tank was fun to get out). Any way..... when i got her running in the tank (we cut the top off a 55 gallon drum and put it under the motor full with water) she would run great but didnt really like to be under 2000 rpm. Took her out on the lake for the first time and it ran great when first started up, then stalled, then started back up and ran okish. wide open it ran great. Now 4 trips out on the way back to the boat ramp, went back down to idle and it died. wont start back up. We let it sit while the traffic died down, and when we tried to start it back it would try, and would run if you put throttle in it but when it came back down below 2000 it die. Got it back to the house, back in the tank, and the same thing happens. Runs ok when its cold but dies when its hot. took the carb apart again and no trash, out new plugs in same thing and no change. Now i have no spark at all, and no voltage to the coils at anytime. Got some test procedures from CDI, and here is what i got. Stop wire is working fine, cranking RPM is great, all engine grounds are good,

Stator resistance
Blue to blue/white (low speed) 5,660 ohms. OEM resistane 3250-3650 ohms, CDI resistance 500-600 ohms
Red to Red/White (high speed) 97 ohms. OEM resistance 75-90 ohms, CDI resistance 28-32 ohms
Trigger coil resistance (purple to white) 866 ohms, OEM resistance 800-1400

DVA readings
Blue to blue/white-256.6 V, CDI specs 180-400V
Red to Red/white- 20.29V, CDI spec 25-100V
Trigger- 1.686V, CDI specs 4V+

We took the trigger out of the equation, and took a signal generator set to 9hz, 4V, and 50% duty cycle (readings from trigger but with the proper voltage) and got spark but not at the right time. So we figure it was the trigger coil, but since the resistance was in spec we thought it was a weak magnet in the flywheel. Found another flywheel, but still got the same voltage. New trigger coil and same thing, and still no spark. ANYBODY HAVE ANY IDEAS???? This thing has me stumped. Even has every boat shop in driving distance stumped. and i dont want to keep throwing parts at it.

Any help would be great guys.

Thanks

 

[Jiggz]

Re: 1995 force 40 no spark

It seems everything is within specs. So the only thing I would recommend checking for now is the connectors on the wiring harness and other connectors for the ignition system. make sure they are clean and making the proper connections. Use contact cleaner if you must. After more than 12 years in storage, the aluminum contacts in the harness connectors are most likely scaled. When I was in the Navy we use to clean those by soaking them in citric acid solution or sometimes in a strong mix of koolaid and then wire brush them.

 

[Dwharris09]

Re: 1995 force 40 no spark

Ill see what i can do, ill try and take the whole harness apart and clean everything. i just really dont want to get rid of this motor, it probably has less than 50 hours on it even with all the running we did. Ill see what i find this afternoon.

thanks again.

 

[pnwboat]

Re: 1995 force 40 no spark

Isn't the low speed stator coil resistance is out of tolerance? If the low speed stator coil is bad, it'll run OK at high speeds but not at low speeds. Kind of describes your symptoms.

 

[Jiggz]

Re: 1995 force 40 no spark

It's the only faulty thing I can think off after you tried using an external input for the trigger signal and there was spark. I do not believe you can discount the trigger entirely yet. While cleaning the contacts, remove the flywheel and do a visual inspection of both trigger and stator, Sometimes the problem is a worn out or cracked wire insulation that is shorting to ground.

 

[Dwharris09]

Re: 1995 force 40 no spark

i didnt get a chance to check the contacts today, my truck took most of my attentions today. But luckily i have tomorrow off too, so ill see what i can find. I've already had the flywheel off a few times before looks at the magnets and everything. Everything looks good under there. Thats why everyone is stumped.

 

[pnwboat]

Re: 1995 force 40 no spark

If you have a switchbox type ignition system, then I would suspect a problem with it. Both the trigger signal and stator voltage go to the switch box, which in turn fires the coils.