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1975 Mercury 150 hp

jhenry72

jhenry72

New member
Hello,
Just looking for a little direction. I've got a 1975 Mercury 150 hp with No spark. I've been researching previous posts and tried a couple different tests. Ultimately what I've found was that I have No power to the coil. There is power going to the switch box but none coming out to the coil. I am New to the Outboard Motor thing so, is this a switch box issue? or do I need to look else where?

Thank you Very much as any info is Much Appreciated!
 
I would start with the switch boxes and the timing ring as that's what pulses the switch boxes to fire the coils.

Are you missing spark on all the cylinders?
 
Well, I've figured out my no spark issue I think... My internal wiring harness is Completely shot! Some connections where only held on by a couple strands of wire! Looks like a New harness is in my Future!

Thanks for All the Help thus far!! Really Appreciate it!!
 
jump 12v to the red and the white on the side of the switch box, crank it over it should spark, also, on the port side of the switchbox on the brown lead, there is a little black switch attached, disconnect that, that is a mercury switch to kill the engine if it tilts up
 
HARNESS??

WHICH HARNESS ,THE ONE ON THE MOTOR OR THE ONE GOING TO THE CONTROLS?? SIERRA AND C.D.I. ELECTRONICS MAY MAKE AN AFTERMARKET.
MY DISTRIBUTER HAS MOTOR HARNESS FOR $199$ FITS 73-77 1500 INLINE 150HP


LATER
CRC
 
I have a brand new Mercury harness, the one under the hood, but try to hot wir it first, make sure it has spark, where are you in Wi? I'm at the wi/il border if you want to bring it over, most times you can carefully repair that harness if the wires are rotted under the hood.
 
I'm in Racine. I already ordered a new wiring harness, and it should be here by April 2nd. The wires were pretty corroded. Some of them were only held on by the electrical tape! As soon as I unwrapped it, they fell off! I'm surprised it even powered it enough to turn the motor over! I did get to do a couple tests though, not sure if the're accurate with the way the Harness was though.. I only had 7.6 volts from the White wire on the switch box when I was told I should have 9.6 volts. And I was also getting 7.6 volts from the brown wire off the Trigger. But, Definitively!! If I have any trouble after installing the new harness, I'd love the help! I am new to this whole outboard stuff and don't need to spend extra $$ if not needed!

Thanks Again! John
 
Ok, I'm at a Loss... I replaced the Internal wiring harness with same results....No Spark. I cleaned ALL the ground wires, checked the voltage from the white wire on the switch box and it reads 9.6 volts while cranking. I checked the brown wire ,one opposite side from the Trigger, and got 9 volts while cranking. Checked the green wire while cranking and also get a very minimal voltage. Not even a whole volt. Seems that I've got power everywhere I need it to be, without getting Spark! Maybe it's time to bring it in....?

Once again, You guys have been Very Helpful thus far! And I Greatly Appreciate Everything!

John.
 
carefull

be sure not to short all your electronics out.if the harness was your only problem and you jump it out to the wrong wires or other wires in the harness are bad you could ruin alot more than just a harness.
 
Good Mechanic??

Well, I think I am going to have to breakdown and find a Good service tech! :shakehead: I'm thinking it's the Trigger but, I don't what to have to buy it and have same results. I've done the jumper wire test on the terminals that the trigger attaches to, on the switchbox, and got the coil wire to spark! So, if Anyone knows of a Good place to go to? I live in South Eastern Wisconsin. Racine to be exact. 53404 area code.

Greatly Appreciated!

Thanks,
John.
 
Hey Bill!
Awesome!!! Thanks SOOOO Much!! Let me know when is a good time to call and set something up. I work 2nd shift in Milwaukee, so I'm home till around 2:00pm.
 
CAll anytime 847 356 3245, I can test the trigger, and if it needs one you arent going to be able to do it.
 
Hey Bill,
I jumped the red and white wires like you said and cranked it over, still nothing. I went from the Positive on the starter solenoid to the red wire, then from the red to the white. I checked and had 12 volts on both wires. Does that mean it Is the trigger or not the trigger?

Thanks Again,
John.
 
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