Merc outboard 50 hp 1987 still isn't getting spark

[RandyS0417]

We bought a 1987 2 stroke Mercury 50 HP that came on the Avon RIB, we were having problems with intermittent starting of the motor. We talked to a few mechanics and we have pulled the flywheel and replaced the Stater assembly, trigger, rectifier. when we cranked the motor it fired up for a few minutes and quit running, upon further examination we noticed we were not getting spark and the original switch box was hot and somewhat melted so we installed today a new switch box, all the new parts are CDI so everything matches. we fired it up and again it ran for a few minutes and it cut off again and we don't seem to be getting spark again. We also replaced the key switch with push choke. we have confirmed all the wires colors match all the connections as they should and I have tested the manual electrical levels with the ohm meter and they are all within the manual's specifications.

I also have replaced the plugs and plug wires.

Does anyone have any idea what else to look for or what the problem could possibly be?

Please let me know.. .. Frustrated Mercury owner..

 

[achris]

Re: Merc outboard 50 hp 1987 still isn't getting spark

First up, throw that damn ohm meter is the bloody bin!!! When, oh when, will people stop trying to fix ignition systems with an ohm meter? I could cheerfully shoot the idiot at CDIElectronics who posted up resistance readings for ignition components!!

Now, I'll get off my soapbox and give you some advise. Buy/build/steal/borrow a DVA meter. ONLY with one of those will you stand ANY chance of properly troubleshooting your ignition system.

Go to this thread and it will take you though building one. If you have a couple of hundred dollars to spend, then buy one from Merc or CDI, your choice.

http://forums.iboats.com/showthread.php?t=374544

Do you have a Merc service manual? (The clymer and seloc ones should join the ohm meter in the trash!) If not, I'll scan and post the test procedure for you....

Chris...........

 

[RandyS0417]

Re: Merc outboard 50 hp 1987 still isn't getting spark

Thanks Chris for the reply, we are only using the merc service manual specs I will have my son build the DVA meter and get back with the results today.