'76 Johnson 6HP (6R76A) spark issue

[Royce Brown]

I purchased a spark tester and indeed confirmed by suspicion that only one plug was producing a spark on my 1976 6HP 6R76A motor.

The motor starts and runs when I manually wind the magneto (currently waiting on new pinion gear to rebuild starter recoil) but only the bottom cylinder is running.

My belief is there is only one coil on this motor, so that means if one plug sparks then the coil itself is functioning, is that a correct assumption? I must have an issue with the spark plug lead/boot labeled "up"? Am I harming the motor by running on only one cylinder?

I can purchase a new lead for a reasonable price ($18), but I've never worked with a magneto before and not sure what I'm getting myself into trying to replace the lead myself (I want to learn everything I possibly can so it's something I would like to attempt).......

I found a service manual on eBay but it's labeled for a 1976 "6R76", my motor is a "6R76A".....not sure what the extra "A" signifies but I assume the manual would be applicable to my motor. Any insight is greatly appreciated.

Cheers, Royce

 

[boobie]

There's two of everything on that motor. Coils, points, condensers and ect. Look up your motor in a parts book.

 

[oldboat1]

If the eBay service manual is an oem manual rather than aftermarket, it would be a good idea to get it if it's in your budget -- pretty scarce. Look closely. It may be a parts manual (less scarce, and also useful). The "A" suffix won't matter.

 

[schematic]

very very common for coil failures on this engine. Don't waste your time. Pop the flywheel off and replaced BOTH coils. You will see the insulation coming off like corn flakes! You can get coils here from Iboats

 

[Royce Brown]

Thanks guys, this seems to be covered in depth in the thread I found after doing some digging. Looks like I need to familiarize myself with removing the flywheel after buying harmonic balancer puller and torque wrench.

https://forums.iboats.com/forum/eng...ge-coils-and-set-points-on-old-omc-s?t=294072

 

[Mohawkmtrs]

...and a strap wrench to hold then flywheel from rotating.

 

[Royce Brown]

...and a strap wrench to hold then flywheel from rotating.

Yes! Just watched this YT video and realized I needed a strap wrench. Now I just need to find some reference on how to reassemble flywheel after changing coils....

https://www.youtube.com/watch?v=faI_fLS6QWU&t=0s&list=PLvK5xaRUtQXoydaCGQTmmZSnxzq_7Ba53&index=3) deta

 

[F_R]

Flywheel and shaft tapers must be clean and dry. Torque nut to 40-45 foot pounds.

 

[Chinewalker]

And, no, the maroon coils from the 1970s do NOT tend to fail regularly. Chances are your points are a bit crusty with age - I'll bet either cleaning the points or replacing them outright, then gapping to .020" will give you a hot spark. Condensers have been known to fail, but by the 1970s OMC had the coils pretty good - much improved over the ones of the 1950s into the 1960s, which are almost always cracked.

 

[Royce Brown]

And, no, the maroon coils from the 1970s do NOT tend to fail regularly. Chances are your points are a bit crusty with age - I'll bet either cleaning the points or replacing them outright, then gapping to .020" will give you a hot spark. Condensers have been known to fail, but by the 1970s OMC had the coils pretty good - much improved over the ones of the 1950s into the 1960s, which are almost always cracked.

I will try cleaning the points before I replace the coils. I assume a voltage meter could be used to test the coils somehow.

Also if I clean the points is it possible to re-attach the flywheel without tightening to verify presence of spark?

Also am I damaging anything by running on one cylinder?

 

[Chinewalker]

Yes, there are some tests you can do with a multi-meter to check a coil. Poking around online you can probably find some resistance specs, etc. for them.

Yes, you can spin the motor over to verify spark without torquing the flywheel on.

No, you're not damaging anything by running on one cylinder, but why would you want to any more than necessary?

 

[Royce Brown]

Yes, there are some tests you can do with a multi-meter to check a coil. Poking around online you can probably find some resistance specs, etc. for them.

Yes, you can spin the motor over to verify spark without torquing the flywheel on.

No, you're not damaging anything by running on one cylinder, but why would you want to any more than necessary?

Because I want to go out trollling while I wait for any replacement parts needed, perch should start biting hard on my lake in the next few weeks and I want to be out on the water, that's why I'd run on one cylinder if it didn't do any harm, other than wasting gas I just need to poke around at slow speed.

Thanks for the help mate!

Cheers, Royce

 

[Chinewalker]

You'd be dumping half your gas right into the water. I wouldn't recommend it. Clean the points and see what happens - no new parts required...

 

[Royce Brown]

You'd be dumping half your gas right into the water. I wouldn't recommend it. Clean the points and see what happens - no new parts required...

Yep I'm going to start with some cleaning and order parts only if necessary. Might be time to bust out the old oars then, thinking about the amount of fuel I use and considering 1/2 of it going straight into the lake isn't the best idea for sure.

 

[Royce Brown]

UPDATE: I finally got all the tools needed to remove the flywheel and inspect coils. It didn't take long to find a frayed wire on the upper coil, which I believe is causing the spark (lack there of) issue.

I also noticed that the plug wire end that connects to the coil appeared to be slightly pulled out from the grommet/spike that connects from the coil, but after pulling the wire through and reinstalling the coil I still wasn't able to produce a spark.

I am ordering a new coil but was wondering if there was anything I could do to jerry-rig the wire? Add some sort of insulation or solder on a new lead? I wrapped it in electrical tape but it still wouldn't produce spark.

Also it appears to me the coil lead was attached to the incorrect terminal, which allowed the flywheel to rub against the wire because of how it was positioned, I attached it to the other terminal and now it's pulled away from the flywheel.

Thanks, Royce

 

[Chinewalker]

It's wired correctly - wire gets tucked down and under the coil laminates, out of the way of the cam. If the wire isn't broken, some good electrical tape can seal it back up.

As for the plug wire, it is pushed into the boot on the coil with a rubber outer sheathing boot slid over it. The center core of the wire has to hit the "nail" end that sticks out of the coil inside the boot.

Make sure your points are clean and gapped at .020" while you're in there.

 

[racerone]

Bonus.-----Your motor has 2 factory new coils to replace the originals that were likely cracked.

 

[Royce Brown]

It's wired correctly - wire gets tucked down and under the coil laminates, out of the way of the cam. If the wire isn't broken, some good electrical tape can seal it back up.

As for the plug wire, it is pushed into the boot on the coil with a rubber outer sheathing boot slid over it. The center core of the wire has to hit the "nail" end that sticks out of the coil inside the boot.

Make sure your points are clean and gapped at .020" while you're in there.

Okay I will try wrapping the wire with some tape and putting it back together to test for spark while I wait for my part to arrive. Getting the plug wire seated in that small boot is a real pain, and my boot was deformed (probably from being installed incorrectly by prior mechanic), really had to work it with my pick set.

The points looks shiny clean and a .020" feeler was a snug fit TDC.

 

[Royce Brown]

It's wired correctly - wire gets tucked down and under the coil laminates, out of the way of the cam. If the wire isn't broken, some good electrical tape can seal it back up.

As for the plug wire, it is pushed into the boot on the coil with a rubber outer sheathing boot slid over it. The center core of the wire has to hit the "nail" end that sticks out of the coil inside the boot.

Make sure your points are clean and gapped at .020" while you're in there.

Well I owe you a beer mate, you just saved me $50! I wrapped the lead in some electrical tape & pulled more of the top plug wire through and trimmed the old end (it looked worn & dirty ~ wasn't confident that I had the coil spike seated correctly) of the wire off and put it back together and now I get strong spark on both plugs! Thank you so much for the great advise.

One last question for you guys regarding putting the flywheel back on; I know it should be clean and dry, but what would you suggest for cleaning the shaft/slot? Just a clean rag? It looks kind of greasy now.

 

[Chinewalker]

Carb cleaner or the like to clean any grime out. Wipe with clean cloth.

Glad you got fire!