no fire on 1979 140 merc

[starcraft18]

engine on 1979 140 merc wont fire i pulled the plug wires off plug and checked for fire it has none what would the most likely cause be i checked the tilt switch it is ok .

 

[tomandkit]

Re: no fire on 1979 140 merc

I'm having the same trouble on my 89 100hp. I haven't been able to check to see if I'm getting spark. You mentioned a tilt switch. Is that the switch that won't allow you to start unless the motor is down? Where is that switch, I want to check mine?
I did talk to a boat repair guy about mine and he said if you're not getting spark it could be a bad stator or coil.

 

[starcraft18]

Re: no fire on 1979 140 merc

take the cover off and it is located on the right side of the switch box
facing the front of the motor

 

[jimmbo]

Re: no fire on 1979 140 merc

No spark on any of the 6 wires? A 79 uses the ADI system, 2 switchboxes, 6 coils, 1 trigger assembly, and 1 stator. Could be a bad switch in the control box, a pinched or open wire.

The mercury switch, also called a tilt switch, is there to prevent over revving if the prop were to leave the water due to the engine tilting up when striking an underwater object. It also reduces the slamming of the engine against the transom.

 

[Chris1956]

Re: no fire on 1979 140 merc

Starcraft18, The orange wire on the switchboxes is the killer wire, which is grounded at the ignition switch to kill the spark. You should remove the orange wire from the powerpacks and see if spark returns. If so, you have an ignition switch or boatwiring harness issue.

 

[starcraft18]

Re: no fire on 1979 140 merc

i may be wrong but i dont see but one switch box on my motor
it is located on the front of the motor in front of the carbs where would the other be located?

 

[Chris1956]

Re: no fire on 1979 140 merc

Hey Starcraft, you got a distributor on that motor and one coil? If so, it is likely an earlier year, and a different troubleshooting procedure.

 

[Tadd_P]

Re: no fire on 1979 140 merc

yeah id say bad distributor or points are bad possibly. I have a 1979 115 OB and it was the first year that they ran the ADI ignition. Check out that distributor and the coil that is most likely your problem. Then check into that switchbox. If the switchbox is out need to find the problem that roached it most likely bare wiring and those motors were nitorious for leaking oil/gas out of the carbs and destroying the wire coatings. Good luck

 

[Laddies]

Re: no fire on 1979 140 merc

If your engine has only 1 switchbox then it has a dist. and is batt powered CD, if it has 6 coils it is ADI CD which is it? We must know to help