1977 70hp johnson not firing

[Fowl_obsession]

ok guys i have a 1977 70 hp johnson that i bought a few months ago. when i bought it it fired up first pull (bad starter so we pull started) we began work on the boat and the motor didnt move for a while. now we are ready to get it on the water and i cant get a spark.

 

[racerone]

????----So do you have spark when you pull it over with a rope today ??

 

[Fowl_obsession]

????----So do you have spark when you pull it over with a rope today ??

no spark

 

[StarTed]

I take it that you put the motor on a different boat from when you ran it. Does that mean it's now on a different wiring harness?

 

[Fowl_obsession]

I take it that you put the motor on a different boat from when you ran it. Does that mean it's now on a different wiring harness?

when we first started it the motor was on a saw horse with nothing more then gas and water hooked up. now i have it on my boat with the original controls. could the throttle controls have something to do with it?

 

[StarTed]

I would suggest you try without the controls the way you did at first. If it runs then reconnect the controls. It may be something like an adjustment or a neutral safety switch. Make sure all the grounds are good. Check at the wire as well as the terminal. There could be corrosion between the wire and the terminal.

 

[Fowl_obsession]

I would suggest you try without the controls the way you did at first. If it runs then reconnect the controls. It may be something like an adjustment or a neutral safety switch. Make sure all the grounds are good. Check at the wire as well as the terminal. There could be corrosion between the wire and the terminal.

could it be something like a neutral safety switch if there is no battery? the only time during all of this that we used a battery was to see if the ignition switch was wired correctly. just for more info, the switch did turn over the starter (which is too weak to do anything but slowly rotate the flywheel) but the push choke did not work

 

[StarTed]

I'm not sure on that but I suspect that the neutral safety switch either shorts or opens the magneto ignition circuit so a battery wouldn't make a difference. You said it ran without a battery so the ignition has to be powered by the magneto in the flywheel. A typical way to stop such a setup is to disable the ignition which the neutral safety switch is designed to do.

 

[racerone]

If the electric starter is bad then the motor will not crank fast enuff to get spark !

 

[oldboat1]

Key switch has to be in the running position if it's wired to motor. If run without a battery, the stator or rectifier will burn out -- no charging, but if the stator is gone the power pack is at risk. Should run it hooked up to a charged battery, whether or not the electric starter is use.

 

[emdsapmgr]

That engine has to crank at least 250 rpm's so that the ignition will fire the plugs.

 

[Fowl_obsession]

so where should i go from here? could i take the neutral safety switch off of the ignitiom switch and try to crank it with a battery hooked up?

 

[oldboat1]

Key switch in the off position shorts the ignition. If you try to start manually with the switch off, you will not get spark.

If you started it manually on the sawhorse, you might be able to do it again on the boat -- but need the key switch in the run position to start and run, even manually starting. Even with no battery. It operates as a kill switch. You may need to turn it faster, as indicated above, but have no chance if the key switch is off.

But if you manage to manually start and run it without a charged battery in the system, you will do some damage.

If it were mine, I would do some work troubleshooting the starting system -- maybe be a minor fix.

 

[Fowl_obsession]

Key switch in the off position shorts the ignition. If you try to start manually with the switch off, you will not get spark.

If you started it manually on the sawhorse, you might be able to do it again on the boat -- but need the key switch in the run position to start and run, even manually starting. Even with no battery. It operates as a kill switch. You may need to turn it faster, as indicated above, but have no chance if the key switch is off.

But if you manage to manually start and run it without a charged battery in the system, you will do some damage.

If it were mine, I would do some work troubleshooting the starting system -- maybe be a minor fix.

can i manually start it with the battery hooked up without doing damage or do i need a new starter before I continue?

 

[oldboat1]

OK to run with battery in place, starting manually. (keyswitch in run position to start and while running -- should be able to shut off the engine with the switch as well). The charging system is meant to maintain the charge, so charge up the battery some first -- might as well give it a full charge and test the elec. start again too.

 

[Fowl_obsession]

OK to run with battery in place, starting manually. (keyswitch in run position to start and while running -- should be able to shut off the engine with the switch as well). The charging system is meant to maintain the charge, so charge up the battery some first -- might as well give it a full charge and test the elec. start again too.

any technique on getting the flywheel spinning fast enough to produce a spark? i cant seem to do it

 

[oldboat1]

If testing for spark, can remove plugs and spin the flywheel by hand or use the manual method you were initially using. With your spark tester hooked up, motor in neutral, key switch in run position, you should see spark. You could also unplug the wiring harness, and spin it -- similar to what you did on the sawhorse (but with the tester hooked up and plugs out).

Spinning fast enough to fire up the motor is a different matter -- presumably were able to do that before if you got it running. Would need to replicate -- but not healthy for the ignition system if you get it to run without a battery or with a dead battery. You didn't have the starter switch connected earlier (no harness), as I understood your description. If you lost spark now using your manual starting method, probably fair to assume it's a key switch issue -- or perhaps the motor isn't in neutral.

Best bet would be to find a fix for the electric starting system, IMO. Can check the starter by briefly jumping it from a good battery. If the starter is operating, need to look for a wiring flaw in the starting circuit. There may be an ignition problem surfacing now, but harder to diagnose without the starting system.

edit. might have misuderstood your post -- moved to testing elec. starting system?