1985 Merc 75 hp ignition problems

Hello all,
Im having an issue with my ignition.
no spark on cylinder 1 & 2
3 & 4 are fine
Is this the CDI,trigger or stator causing this?
It ran the day before on 4 cylinders for 15 minutes,then it bogged down like it shut down 2 cylinders...
any suggestion on where to start?
CDI serial # 332 5772A1

Re: 1985 Merc 75 hp ignition problems

Odds are that it's not the stator. (but you can ohm check it easily).

Then, ohm out the trigger as per the manual and eliminate it. Only the switchbox will remain.

-W

Re: 1985 Merc 75 hp ignition problems

Sweet a question I can help with!!

I have an 86 Merc75 and I just fixed a similar problem.

Look for jacked up (disintegrated wires) on the stator and trigger. If they look good test both parts. Do a search here for the instructions. Also test the rectifier. I bet that part is toast, I know mine was. The wires on my stator and trigger were really bad and that lead to my switchbox dying too. I had no spark on #3. I replaced all these parts and now it runs like a champ. The aftermarket CDI parts are supposed to be better than the Merc parts so they should hold up better. Keep me posted...
P.S. CDI is a brand name-what part are you refering to when you say CDI?

Re: 1985 Merc 75 hp ignition problems

Clams Canino said:

Odds are that it's not the stator. (but you can ohm check it easily).

Then, ohm out the trigger as per the manual and eliminate it. Only the switchbox will remain.

-W

Click to expand...

Thanks Clams,
i ohmed out the trigger and it was fine---shielding not so good
I tested the stator and found the red wire test showed high numbers over the alotted scale
It also has shabby looking shielding.
do i need a special puller for the flywheel?
Also.how do you mark the flywheel so you get it back on properly?


Mike

Re: 1985 Merc 75 hp ignition problems

You can get the special merc puller but I pulled mine used a regular harmonic balancer puller. I used an air impact gun the drive the puller bolt though. It was really on there. I pulled two of the bolts from the middle of the flywheel and screwed the puller's bolts in there. Worked fine. The hub is under there and I felt like it was plenty strong. The flywheel only goes on one way, it is indexed with a little notch so it is actually an easy job. Pulling the flywheel was the hardest part. Anything else let me know, I just did mine recently and we have the same motor.

Re: 1985 Merc 75 hp ignition problems

Thanks for the info guys,i appreciate it.
BTW.....is 140 compression on all 4 cylinders good for this motor ?
this was the reading i checked tonight.