Mercruiser 140 with Pertronix issue, no spark.

[tigger3650]

I seem to be having the same exact problem with my 140. It is wierd how this just starts (or in regards to the motor doesn't start) one day out of the blue. I read all my voltages and am puzzled:

I disconnect all wires from the (+) side of the coil, I have a purple-ish wire from the choke, a purple-ish/ red-ish wire from the ignition switch, and a pink w/ yellow stripe to the starter and a red wire to the prtronix ignitor.

With the key "on" I get 12v from the ignition wire to ground.

When I hook all the wires back up, starting with the ignition wire, I keep 12v until I hook up the red wire for the pertronix ignitor. When I hook it up to the coil, voltage drops to 4v.

I jumped a wire from the (+) of the battery to the (+) of the coil and vroom, fires right up. Pull the jumper off, motor dies.

I am going to run a jumper from the ignition key to the coil tomorrow and see if this cures the problem.

Any other suggestions?
-Mike

 

[stonyloam]

Re: Mercruiser 140 with Pertronix issue, no spark.

If you have a stock coil, the purple wire from the choke to the coil is your resistance wire that drops the voltage to the coil. The Petronix needs a full 12V to work properly. You can pick up 12V by splicing the red petronix wire into the purple wire from the from the ignition switch to the choke connector. Your plan to run a wire from from the ignition should work OK. Good luck.

 

[tigger3650]

Re: Mercruiser 140 with Pertronix issue, no spark.

Update:
Ran the jumper from the ignition switch to the positive side of the coil. Works perfect. Replaced the original wire with a new one and now the boat starts easier than it ever has. Now I have a brand new fuel pump (initially thought this was the problem) that I don't need....yet...

 

[stonyloam]

Re: Mercruiser 140 with Pertronix issue, no spark.

If you are using a wire from the ignition to the + side of the coil, and if you are using the stock coil you are putting too much voltage to the coil and it might get very hot. If you are using the stock coil you need the resistance wire in there. And you need to continue to feed the full 12 volts to the Petronix. IMHO you should get a Petronix Flamethrower II coil and leave the wiring as is with 12 volts to the coil and the Petronix. The reason it works well now is the fact that the Petronix unit is seeing the proper voltage.