1971 Mercury 7.5 ignition problems

[cmeilleur1337]

Hi all. I am kind of new to this outboard thing, so bear with me. I recently picked up a a 1971 Mercury 7.5Hp with known electrical issues. It was purchased as a spare /parts motor for the 1974 Merc 7.5 I bought a few weeks ago. Now, i bought it sight unseen, under the pretense it was a 1975. Turns out, it is a 1971, so I am not sure what is cross compatible. The 1974 used a CDI ignition (CDI was just replaced on it).
So, now I am left troubleshooting the older '71. I am not finding to much info on testing for the coils and stator. When i started meddling with it, I noted some weak spark on 1 plug, and after a few pulls, I have no spark on either.

What is the test procedure for these coils? They are green coils marked with "336-4409 B". Also, if they do need replacing, what is the compatible part number?

On the Stator side, What are the readings / test procedure for that. There is a ground wire from the stator to the breaker/ points mounting plate, an orange wire ( to the stop sw) and a green to the ignition coils.

I also noticed there is no condenser. is this normal for this type setup?

 

[RCO]

Disconnect the kill wire first to eliminate that as a possibility. Have you cleaned and adjusted the points? The resistance on the stator should be 3200-4000 ohms. Not sure on the coil offhand, but the resistance should be close to one another since it's unlikely they are both bad. I don't think there is an aftermarket coil for the Phasemaker ignition, but I could be wrong. The current Mercury part # is 336-4409A4.

 

[Chinewalker]

Also, check the wires for the points at the magneto, as they are known to deteriorate with age to the point of crumbling. The points themselves to generally get a little burned on the Phasemaker mag - that's normal. But if the mounting blocks are cracked, they can arc out. Doesn't hurt to clean the points, in any case. If they're really bad, new ones are available - for a price. Just hope the "donut" isn't bad, as they're worth more than the motor...

 

[racerone]

Is the kill switch circuit normally open or closed on these ???

 

[60sboater]

It is NC and opens when pushed.

 

[racerone]

Well---Post # 2 mentions disconnecting the kill switch.----Not the correct thing to do on these ignitions.

 

[cmeilleur1337]

Well, I get 2 different readings from the coils. And as for the stator, I get verry high resistance in one direction (in the Meg ohm range , and nothing in the other direction. Definitely not in the K ohm range.

The insulator blocks do look like they have seen better days. Also a few cracks in them . I know that they can arc out to chassis, which would cause issues. I am wondering if that could have caused the stator and coil to fail. And yes, the point do need cleaning. Any tips on that?

 

[cmeilleur1337]

Also, I can pickup a whole running power head with electicals, for 125 Canadian pesos. May be worth it if the stator is bad on this one. Cheaper then a replacement.

 

[60sboater]

It may indeed be cheaper. I spent over $200 fixing the stator and wiring on a '73 110 Phasemaker. The ignition coils were good.