1973 85 hp Needs Ignition Help

[JDusza]

Hi. Working on bringing back what is either a 1973 85 hp or a 1972 80 hp, serial number 3741459. Maybe someone can clear that up for me. The data table I found at maxrules.com holds this serial number under both engines. In any case, it is a 4 cylinder, twin carburetor, distributor ignition unit.
The old harnessing was indescribably bad. I have replaced the helm wiring harness, the engine wiring harness and the stator. Harnessing appears to be good to go with the starter relay and starter working and the choke solenoid working. I have no spark at the plugs. I am now approaching the switch box and ignition coil. I have questions on each.
Switch Box: When taking a meter to the inputs and outputs, I verified 12 volts input on the starboard side. I find continuity between the top two posts (the top one and the middle one) of the distributor side (port side). A dead short. I'm not electrical but it seems that outputs should not be shorted together. Is continuity between these posts supposed to be? Both of these switch box outputs go to the distributor.
Ignition Coil: I find continuity between the coil input (coming from the switch box output) and ground. Again, a dead short. And again, it seems that you would not want a dead short between the device input and ground. Wouldn't the input current from the switch box be shunted to ground rendering the coil useless?
I am on my way to find a service manual to find out how to diagnose these components but thought you might give me a couple quick answers pointing me in the right direction.
Thank you. I appreciate the help.
J
p.s., how to you turn off a 1973 model 40, 4 hp, single cylinder? Got the throttle all the way down and she purrs like a kitten. I'm choking it to kill it but that just feels funny.

 

[Chris1956]

There is a troubleshooting procedure for your ignition on the CDIElectronics web page. It will assume the coil is good, and test everything but the trigger. if the test produces spark, the trigger is suspect.

Note: You need to have +12VDC on both the red terminal of the switchbox and the adjacent white terminal on the switchbox. Without this voltage, you will not have spark. Also, the coil is pulsed by the switchbox, so there is no voltage on the coil, normally.

 

[merc850]

Here's the wiring diagram for the 4 cyl. engines, the BROWN terminal is for the Merc tach [NLA] check the timing belt to see if it is OK ie; turns the rotor, don't pull the plug wires out of the cap - they screw in.
Do not try to pry off the rotor in the dist. it is molded on - you can clean the dist. contacts with emery paper if they need it. Make sure the battery you are using is fully charged (12.7v or more) and the cables are clean and tight.
The plugs for that motor are L77V Perma-Gap

 

[JDusza]

Thank you for the input. I have the wiring diagram and believe I am all okay.
I have voltage reacting to the ignition switch and feeding the switch box.
I'll go peek at CDI. For some reason, I didn't think of them. They have been helpful in the past.
I'm wary of the pulse from the switch box to the coil going directly to ground. I could look at the green wire for a signal. That should tell me at least whether it's feeding the coil. Any idea what that pulse should be?
Cheers!
J

 

[Chris1956]

The pulse is very short. I would therefore think you would need an o-scope to see the pulse to the coil. Maybe a DVA would also work.

 

[Faztbullet]

The pulse is very short. I would therefore think you would need an o-scope to see the pulse to the coil. Maybe a DVA would also work.

You can see it with a analog meter