Hi,
I have a 1970 Johnson 85hp that's a tough little engine with good compression (115 min, 120 max.), rebuilt carbs, etc. It runs great when it runs, but twice now it has stranded me without warning. No spark at all.
After the first incidence, I decided to completely rewire the motor, including a new ignition switch, since the original wiring was a spongy mess. (I also simplified it down to the bare bones for what I need, which is basically just wires for "start" and "run".) I now have good voltage from the ignition switch in the ignition "on" (12.9V) and "crank" (10.9V) positions.
After learning the hard way that the light bulb test is the only way to test for amplifier output to the blue wire (feeding the coil), I found that I did get a light every time I manually grounded the amplifier's white/black wire (from the points). But with the points connected, no glow....not even a very faint one. So I checked and regapped the points again, which were fine and clean, and checked continuity of the points as I turned the flywheel by hand, and they were making and breaking perfectly.
To shorten a long story, I bought a used amplifier, and it also gave output when manually grounding, but not through the points. So I ended up going back to the original amplifier, and it worked! Ran fine for a couple of days, in fact. Then it died again. So I'm back to this situation....
1. Amplifier causes light bulb to glow when manually grounding black/white wire (from the points).
2. Amplifier will not glow with points hooked up, cranking engine with the starter.
3. Points are clean, gapped at .010 max., and check perfectly for continuity as the flywheel is turned by hand.
Any theories? My wire connections are all new, and perfect as far as I can tell....but maybe I'll redo the one from the amplifier to the points.
Do you think it's voltage related: i.e., in the "on" position the amp. is being fed 12.9V, but only 10.9 during cranking. Could it still be that my amplifier is weak. Can they "come and go" and run sometimes, but not others?
Thanks for your help and suggestions,
Mike in Iowa
I have a 1970 Johnson 85hp that's a tough little engine with good compression (115 min, 120 max.), rebuilt carbs, etc. It runs great when it runs, but twice now it has stranded me without warning. No spark at all.
After the first incidence, I decided to completely rewire the motor, including a new ignition switch, since the original wiring was a spongy mess. (I also simplified it down to the bare bones for what I need, which is basically just wires for "start" and "run".) I now have good voltage from the ignition switch in the ignition "on" (12.9V) and "crank" (10.9V) positions.
After learning the hard way that the light bulb test is the only way to test for amplifier output to the blue wire (feeding the coil), I found that I did get a light every time I manually grounded the amplifier's white/black wire (from the points). But with the points connected, no glow....not even a very faint one. So I checked and regapped the points again, which were fine and clean, and checked continuity of the points as I turned the flywheel by hand, and they were making and breaking perfectly.
To shorten a long story, I bought a used amplifier, and it also gave output when manually grounding, but not through the points. So I ended up going back to the original amplifier, and it worked! Ran fine for a couple of days, in fact. Then it died again. So I'm back to this situation....
1. Amplifier causes light bulb to glow when manually grounding black/white wire (from the points).
2. Amplifier will not glow with points hooked up, cranking engine with the starter.
3. Points are clean, gapped at .010 max., and check perfectly for continuity as the flywheel is turned by hand.
Any theories? My wire connections are all new, and perfect as far as I can tell....but maybe I'll redo the one from the amplifier to the points.
Do you think it's voltage related: i.e., in the "on" position the amp. is being fed 12.9V, but only 10.9 during cranking. Could it still be that my amplifier is weak. Can they "come and go" and run sometimes, but not others?
Thanks for your help and suggestions,
Mike in Iowa