johnson 85HP no spark

[djwalters]

I just purchased a 1969 Johnson 85 HP model #85ESL69M that supposedly ran. Upon trying to start it, I discovered it has no spark to the plugs. I pulled the flywheel and the points look great. The 2 wires that run down to the Amplifier from the points had rotten insulation and were bare in many places causing them to touch each other so I replaced them with new wires. This did not help the no spark problem. The amplifier has power to it on the purple wire, but I can not get a reading leaving it except a small amount of voltage that runs up the black wire to the points ( This wire is the only wire with a spade terminal end and quick disconnect) There is a blue wire that connects to the coil but no power there at all? Even while cranking the engine over. I believe that makes the amplifier the problem, but how can I test the amplifier to make sure it is the problem? They are very costly, and I don't need a spare if mine is OK. Any other thoughts / suggested tests, will be greatly appreciated. Thanks so much, Dave

 

[WillyBWright]

Re: johnson 85HP no spark

Turn the flywheel until #1 piston is at top dead center (or close). Remove #1 sparkplug and let it rest on a decent ground with the sparkplug wire attached. Turn the key on. Take the wire that leads to the points and lightly rub it to ground with the key on. You should get spark. If not, it could be the coil, but more likely the amplifier. If you do it at night, you might be able to see a leak where the spark travels instead of to the sparkplug.<br /><br />I'm in the middle of an experiment. I bought a Ford control module from the local farm and barn for $16. I have a 12v coil from an old motorcycle (automotive coils cost about $11). I'm substituting those for the original amp and coil on my 1972 100Hp Evinrude. It also uses an amp, but a sensor instead of points.<br /><br />I connected it up tonight and I get spark when I turn the key off. That also happens with original parts. But I'm not getting spark while cranking ... yet. That system's sensor resistance is from 400-800 ohms. The sensor on the outboard specs out at 4-8 ohms. Tomorrow I'm going to Radio Shack for a 100 ohm resistor to connect in series to see if that will compensate. This may not work for your points system, but... Stay tuned.

 

[tashasdaddy]

Re: johnson 85HP no spark

had a 69 115, had to replace amplifier 3 times in 10 years.

 

[philfloating]

Re: johnson 85HP no spark

I had the same problem with corroded wires! I replaced the amp on ebay for hundred bucks "new"!<br />I seen go as high as 300 so shop around! My understanding is that what makes them go out is not a high enough amp battery or not a good charge, loose or corroded connections. These things will make it go out right now. There is away to change the system using an old automotive coil that some members on this board have discussed before! Replace the corroded amp one way or the other or get some good oars!

 

[djwalters]

Re: johnson 85HP no spark

Well what do you know!!! Willy was right on!!! Did the test as described and got spark after several strikes of the wire to ground. Put it back together then lost it again when I tried to start it. Next time I kept sparking it to try and duplicate run time. Kept this up for a few minutes to get things loosened up. Put it all back together again and she fired right up and idled. Problem solved. Thanks so much to all of you, Dave