No spark on 1977 Mercury 150

mnmfors

Petty Officer 2nd Class
Joined
Nov 18, 2001
Messages
176
Hello again everyone,<br /><br />I have a manual on the way, but I just couldn't wait to do some testing.<br /><br />This motor has the old distributer type ignition. I replaced the starter selonoid (as it was missing) Checked all grounds and connections, replaced some ground cables. Then I did the following tests....<br /><br />1. I tested the battery......12.5v<br /><br />2. Tested all ground terminals, replaced a few that looked cruddy, and cleaned terminals<br /><br />3. I got the engine spinning over real good and checked the stator wires...read 7.0 on the ac setting.<br /><br />4. Tested for voltage at rectifier.... 10v<br /><br />At this point I belive that stator and rectifier are good. <br /><br />5. Then came the switchbox...not being sure what to test, I spun the engine over and got 0v on the oposite side of the switchbox (distributor side) nothing on any of the three<br /><br />I am guessing I need a new switchbox. <br /><br />6. I tested for voltage on the + side of the coil and got no voltage. there is a green wire which looks like a replacement someone made, but is in good shape, but I dont know if it should be green. This wire is conected to the entrance side of the switchbox, on the top terminal.<br /><br />Is it safe to hook up a hot wire to the coil and test for spark? Like hotwiring an old car?<br /><br />Any help on this would be greatly appreciated.
 

mnmfors

Petty Officer 2nd Class
Joined
Nov 18, 2001
Messages
176
Re: No spark on 1977 Mercury 150

Also, is there a way to test the distributer without taking it off or apart?
 

mnmfors

Petty Officer 2nd Class
Joined
Nov 18, 2001
Messages
176
Re: No spark on 1977 Mercury 150

I know someone here has at least a little experience with these type ignitions. Any help would be appreciated. If not, I guess I will just wait on the manual.
 

CptNub

Recruit
Joined
May 20, 2009
Messages
1
Re: No spark on 1977 Mercury 150

Hi MNMFORS,

I have the same exact issue. Spark Plugs Are Good, Carbs Were Just Rebuilt, Gas Is New, Starter Works, but I'm not getting any electric from the Coils. My father is an electronics engineer and knows how to read electrical diagrams blindfolded but, I cannot find any electrical diagrams anywhere. The other issue that we have is our electrical configuration is very choppy, it doesn't look like factory wiring at all and we are afraid that its all wrong. Do you happen to know where I can take a look at an electrical diagram for a (1977 Mercury 1500 Power Trim)?

Thank you for your time!

Kind Regards,
AG
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: No spark on 1977 Mercury 150

Here's a simple test for the system.
scan0002.jpg
 
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