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1977 150hp inline 6 no spark

R

Rolly1

New member
I have a 1977 Mercury 150hp inline 6 that has no spark. I replaced the coil and trigger and still no spark! I'm just about at my wits end. I had replaced the stator due to the wiring insulation breaking down and the motor started. Then did the impeller and couldn't get the motor to start again. I disconnected the Mercury switch and still no spark. Replaced the coil and still nothing. The guy I get my parts off told me it's the trigger so I replaced that too. Does anyone know how to test the switch box or any other help please? This is getting expensive and I wanna go fishing! Thanks
 
Stator has nothing to do with ignition on this model...make sure you have 12V on red and white wires on switchbox when cranking.
 
..."I replaced the coil and trigger and still no spark!"

Isn't there a distributor for this model? If so, no trigger coil setup. I'm confused.

Jeff
 
Jeff, this model has a cdi ignition. Distributor has a trigger plate instead of points. I think I have a broken wire in the external wiring harness. Still more testing to do. I don't think this is the main reason for no spark as I ran wires from the key start directly to the switch box and still no spark.
 
  1. Connect a spark gap tester to the high-tension leads coming from the distributor cap and set the gap to approximately 7/16".
  2. Align the rotor with #1 spark plug wire. Disconnect the trigger wires and connect a jumper wire from the white trigger terminal to the black trigger terminal on the switch box.
  3. Connect another jumper wire to the brown trigger terminal turn the ignition switch on. Strike the jumper wire from the brown terminal against engine ground – (DO NO HOLD THE JUMPER AGAINST ENGINE GROUND!). (Or use a CD Tester). Only the #1 spark plug wire should fire. If another spark plug wire fires, there is a problem in the distributor cap
  4. If unit fires switchbox is OK.
 
Thanks very much for your help gents! I replaced the external harness and gave the ignition switch a good spray with contact cleaner started first go! Now I've just gotta get her down to the water to adjust the carbies as she is idling a wee bit high. Pretty sure it's cause of the new trigger as the old one was just about shot. Many thanks again! Hope to have her out fishing next weekend.
 
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