1971 johnson 50hp has weak spark still! Any ideas???

[Aluminum magnet]

Finishing up the season here in Michigan on a dismal note. Had the 50 hp (50esl71) running well, (several trips out) but as soon as the family climbed aboard, she sputtered and died. She tried to restart, and once kept running, but as soon as we left the dock, she quit and wouldn't restart.:facepalmquite the show for the peanut gallery that day) Got home and found a very weak spark. Troubleshot it down to the power pack using a DVA which showed the voltage to drop from 500 off the pack, to nothing when connected. Decided to go with new CDI everything (pack, stator, sensor & tool) While installing, found rectifier bad. replaced that and tested shift diodes good. Found the new pack from CDI bad and returned it for replacement. Also found new CDI sensor rubbing on chamfer of the flywheel like it is too tall !? Sent that back for waranty. DVA's are good now, but the spark is still tiny, and she won't start. double checked and added grounds. checked and rechecked coil wires and connections. I have a 60hp 3 cyl and comparing the two sparks is like day and night. One makes an audible snap and bright blue, the other you can't hear and can't see during the day. Any ideas? The old 1960 Holiday just wants to splash around one more time before going to sleep for the winter. Thanks P.S. Already gone through the fuel system several times, nothing amiss there.

 

[boobie]

Re: 1971 johnson 50hp has weak spark still! Any ideas???

If it was my mtr I'd look at it as though I've never worked on it before and start from scratch with the trouble shooting procedures. Just a thought.

 

[64osby]

Re: 1971 johnson 50hp has weak spark still! Any ideas???

Did you replace the plug wires or at least cut back the wires and reconnect at the coils and plugs?

 

[Faztbullet]

Re: 1971 johnson 50hp has weak spark still! Any ideas???

If both cylinders are sparking, the trigger and pack are working just the output is low and this is a stator problem. DVA your stator output to pack.

 

[Aluminum magnet]

Re: 1971 johnson 50hp has weak spark still! Any ideas???

Thanks for all the helpful ideas. I did cut back the spark plug wires (replaced one) and reconnected the ends. I remember thinking the coils ohm's was low (19-20,000), but I may just be used to point and condenser coils. I do still have 400-500 volts (DVA) on the brown wire from the stator while it is connected to the pack. I am back at it this morning. Thanks for giving me hope to start over, I was ready to throw in the towel.

 

[Aluminum magnet]

Re: 1971 johnson 50hp has weak spark still! Any ideas???

Well' took everything apart again and tested all wires and measured resistances. Put it all back together hoping for a different result. (the definition of insanity, right!) This time I have a muck better spark. The one thing I changed was the coils. I had an old set lying around that had started to crack, but still tested good. I'll have another go at running it tomorrow. Anyone have a good way to dynamically test a coil? As opposed to simply checking resistances.

 

[boobie]

Re: 1971 johnson 50hp has weak spark still! Any ideas???

Most older OMC dlrs do have coil testers for checking them under load. That's the best way other than just replacing them.