Mercury 650 Intermediate spark, now no start

117rb

Recruit
Joined
Sep 7, 2020
Messages
2
Hi, im new here and hopefully someone more experienced can help me.
I have a mercury 650 early 1970s model. I repaired a few mechanical things and got it running great on the hose, buttoned everything up and let it sit a few days. Went back, started it up ran a few cycles and died. No spark. Looked at a few things, tested it and nothing. Tried again next day and did the same thing, ran for 30 seconds and died no spark. Ive got power to the cdi everywhere i should exept the brown wire to the coil. I dont have a dva, should i see any voltage when cranking? I checked the ignition switch thats working. I replaced the coil just to illuminate it. Now after the coil swap and getting the cdi rehooked up and turning over the motor to see if i have spark my starter and electric choke wont work. Ive tried jumping the starter selinoid. As soon as i connect the two post the voltage goes from 12v to 0v. Any help or tip would be greatly appreciated. Ive been at this a few months.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,558
Gee, sounds like the quick disconnect electrical is dirty or broken, cutting off the voltage to the motor.

You might repost this in the Merc outboard Forum.
 

117rb

Recruit
Joined
Sep 7, 2020
Messages
2
sorry dont have serial number because id have to dismount the outboard from the boat to see it. Its a 3 cylinder. New find today, starter is fine, ive found by watching the spark plug that ill have spark for 3 revolutions or so and will lose it, then once more after i stop cranking. Guessing its a loose wire that disconnects when the engine shakes. Any ither theories would be appreciated.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,558
A lot of those engine harnesses are loosing insulation by now, if they have not been replaced. Replacement is recommended.

The quick disconnect boat harnesses can also go bad, at this age. A good test would be to disconnect the boat harness and directly connect the battery to the motor. If the engine harness is still good, you can easily jumper the ignition and see if she has good, consistent spark.

However, If you do not know how to jumper the ignition, I do not recommend it, as you can possibly damage some expensive components.
 
Top