85 horse Merc w/no spark

[McMudpuddle]

New to this forum today! I have recently purchase a 94 Intruder hull with an older Merc, 85 horse, with a pump. The whole thing has been neglected and comes in a kit form. My question today seems simple, but? There is no spark. It is a four cylinder with electronic ignition, probably late 70's early eighties. The tech I have used in the past is now about 70 miles away, so I am turning here for advice. He told me to test the switch box. anyone know how to do this? or where I can get a flow chart that would outline the test sequence? Thanks

 

[ricksrster]

Re: 85 horse Merc w/no spark

What is the serial number? It is on the transom mounting bracket. It sounds like you have a 1976 or 1977. The serial number will help with the year and how to check ignition. Do you have four coils?

 

[McMudpuddle]

Re: 85 horse Merc w/no spark

number 4592000. You are correct, 4 coils on one side of the motor and one electronic box on the other side. Thanks

 

[dchris]

Re: 85 horse Merc w/no spark

Merc 850 85 4590512 thru 4831998 1977
You need a book and ohm meter. It could be the switch box ($250) Stator coil ($150) Trigger coil or rectifyer. There are a few other less likey items. Mine ended up being the Stator coil and rect.

 

[ricksrster]

Re: 85 horse Merc w/no spark

First. Disconnect the kill wire (Orange) on the switch box. It is on the middle post, left side of the switch box. See if you get spark. If you do then you have a bad Mercury switch or their is a short in your wiring harness or ignition switch.
If you still don't have spark disconnect the blue and blue/white wires from the switch box and check the resistance. You should read 5800-7000 Ohms. Then do the same with the Red and Red/White wires. They should read 135-165 Ohms. If you don't get these readings you have a bad stator.
Now disconnect the Brown and White/Black wires on the other side of the switch box. Check the resistance. You should have 800-1400 Ohms. You should have the same readings with the Purple and White.
On the coils the resistance should be 1 Ohm or less on the primary side and 800-1100 on the spark plug wire side.
If every thing checks out you probably have a bad switch box.

 

[McMudpuddle]

Re: 85 horse Merc w/no spark

Thanks I will give it a go!

 

[McMudpuddle]

Re: 85 horse Merc w/no spark

Thanks for the help. Turned out to have a bad stator and a bad switch box.
Do these components generally go out at the same time, or am I just lucky?

 

[ricksrster]

Re: 85 horse Merc w/no spark

If your stator is bad, wait until you replace that before you change the switch box. You can;t really tall if the switch box is bad if you have bad stator.

 

[McMudpuddle]

Re: 85 horse Merc w/no spark

With the new stator it ran but only for a short time on all cylinders, then it started dropping two. one new switch box later and all is good.

 

[ricksrster]

Re: 85 horse Merc w/no spark

OK. Boat on!

 

[emckelvy]

Re: 85 horse Merc w/no spark

Just had a similar experience with a '76 ADI 850; no spark, replaced burnt stator, then it had good spark except #3. Replaced switchbox and all was well.

The rectifier was burnt-out too, so that's a good thing to check when doing the ign work.

If you have a tach and it works when you're done, you should be Good To Go.

Otherwise, check static battery voltage with a meter then check again when it's running. Should be higher, and rise when running up the fast idle lever a bit. The Radio Shack rectifier for under $5 is a good choice if the rectifier is fried.

Happy Boating........ed