1985 75hp Mercury not working

[marzoid]

Mercury 1985 75HP



I had it running this summer on the water. It ran great.

It would shutdown in idle tho so I attempted to fix it. The motor would only run when I had it going forward out of idle.



I cleaned the carbs and set the idle speed.

After doing this, it still would not run in idle. But would run fine when I accelerated.

I tried playing with the idle speed a few more times.

After this my motor began to have a harder and harder time to turn over each time.

Until it eventually it would not turn on at all.

My trim would still be able to move up and down



I had someone come check it out.

- compression was good

2 of the spark plugs didnt seem to have spark the other 2 did

we found 2 wires that were in bad shape that ran from the stator(sp?) to the (fly wheel area)

I replaced the wires in that bad area
Now my motor does not have any power going to it at all

The battery is okay



Looking for some help...I live in ontario

 

[marzoid]

Re: 1985 75hp Mercury not working

I should also add that I sprayed carb medic into the carbs as it ran. After this my motor slowly had a harder and harder time to start

 

[canoemang]

Re: 1985 75hp Mercury not working

So after fixing the stator wire you had good spark on all 4?

Did you change/clean your plugs after you ran that carb medic through it?

 

[Silvertip]

Re: 1985 75hp Mercury not working

Have you checked the plugs AFTER you sprayed the stuff into the carbs (which does nothing to clean the INTERIOR passages in the carbs). Only disassembly will allow thorough cleaning. By the way -- lets use correct terminology so we understand each other. The starter is what "turns over the engine". The engine can turn over -- but not start. To say the engine "does not turn over" means the starter is not spinning the engine (flywheel is not turning).

 

[marzoid]

Re: 1985 75hp Mercury not working

After I changed the wire I lost complete power to the motor. I made sure the connection was good (I will be redoing my work this weekend just to be sure) I'm thinking of replacing the wires all the way up (they go up into the fly wheel area....which means I would have to take the big nut that holds the fly wheel in place off (in the center of the fly wheel). Am I going to cause more problems by doing this?)

After I ran the carb medic through it, I have looked at the spark plugs and have tried another set of spark plugs. And both sets result in only the top 2 spark plugs to have spark. The bottom 2 do not.

Silvertip to clear things up... After spraying the carb medic and putting everything back together. I tried starting the motor. At first the starter did work it would turn the flywheel. But after a few more starts it seemed like the fly wheel had a harder and harder time turning. Until eventually it would not turn at all.

It seems like me working on the motor loosened something up and made the electrical system in this motor worse.

Someone said it may be the powerpack? or coils is this a possibility?
There are so many avenues it could be. I just want to narrow it down. I really appreciate all your help

 

[CharlieB]

Re: 1985 75hp Mercury not working

You got to be very careful spraying anything into the carbs other than pre-mixed fuel. None of the spray cans have oil to provide lubrication and can cause damage to the bearings, and pistons rings, leaving the engine worse for wear. Check compression on each cyl, hope they are very nearly the same.

As for the lower two cyl not sparking, you may have a faulty trigger, not telling the ignition switchbox to fire. Since there is NO RETURN on electrical parts, and they can get expensive fast, PROVE THE FAULT before ordering any parts.

CDIElectronics has an excellent Ignition Troubleshooting Guide available for FREE download on their Support page. Get it, find your ignition system, follow their detailed steps to troubleshoot your ignition and determine the exact cause of the problem.

Repost any questions, problems, or anything you don't understand, we will help walk you thru it.

 

[marzoid]

Re: 1985 75hp Mercury not working

i got the boat power back
the trim now works!
and the fly wheel will turn but will not start the motor
what should I check?
im going through the cdi guide now

 

[half a can]

Re: 1985 75hp Mercury not working

What did you do to get power back? Mine just did the same thing this morning. the starter quit and the trim won't push the motor up. Both issues happened at the same time so I am guessing they may both be related somehow. Thanks.

 

[marzoid]

Re: 1985 75hp Mercury not working

Hey I think I had some kind of loose connection in the controller (where key goes in)
check your battery also

 

[marzoid]

Re: 1985 75hp Mercury not working

what do i do if im getting spark on all 4 spark plugs?
but boat wont start>?
fly wheel is turning
im so close!

 

[marzoid]

Re: 1985 75hp Mercury not working

it was my harness wire that ran to coil 1 and 2
just incase someone else runs into this problem