Johnson 6hp issues Aggghh

[Maxamus137]

I've got a 1969 johnson 6hp. I've done a carburetor kit job on it, it runs here at the house but when I get on the river, it either wont run at all or it only runs for a short time or it only runs about half and jumps... Help I'm at my wits end. All houses replaced and fuel pump replaced.

 

[oldboat1]

"runs about half and jumps"? Could be important -- need more explanation.

 

[Scott Danforth]

could be cracked coils. however agreed, needs more explaining.

 

[Maxamus137]

The motor will run at about 1/2 power and then rev up quickly to full power and ho back to half power. But it seems like when I'm at home it runs fine. Then at the river. It either wont start at all or only runs half power.

 

[Maxamus137]

The motor will run at about 1/2 power and then rev up quickly to full power and ho back to half power. But it seems like when I'm at home it runs fine. Then at the river. It either wont start at all or only runs half power.

 

[racerone]

Pull the flywheel and inspect the coils !------They are either new or both cracked and need replacing.----Answer this, does spark jump a gap of 1/4" or more, yes or no?

 

[Royce Brown]

I would suggest buying a $6 inline spark tester from your local auto parts store, check to see that spark is getting to both plugs first.

Also consider reading through the info below, it helped me a bunch in understanding & diagnosing my 6HP motor, along with the wonderful people here.

http://www.leeroysramblings.com/OMC_6hp.htm

 

[Maxamus137]

I dont have a spark tester but will get one. Your idea of cracked cool makes sense, when it sets here for awhile the cool sets and makes good connectivity, but when transported it opens the crack and doesn't work. I'll pull the top off and check. I'll post my results, Thanks for the ideas. GREAT FOLKS HERE.

 

[Chinewalker]

Probably NOT the coil - by 1969 they had sorted out the cracking coil issue and they rarely cracked by that point. The original 1969 era coils were kind of a maroon color and were quite stout.

More likely your points are dirty and need a thorough polishing and re-gap to .020". If the coils aren't visibly cracked, they're probably okay. Other possibility would be the condensers. In any case, it certainly sounds like you're running on one cylinder, and running in a barrel at home it is very easy to miss as those motors will run quite well on one cylinder.

Pull one plug wire at a time and note any change in running characteristic and I'll bet you'll find with one wire pulled, no change, and with other, the motor stops entirely.

 

[Maxamus137]

Yep both cracked !!! I'll let you all know how it turns out. Thanks So Very Much. You all are Fantastic.

 

[Maxamus137]

[No message]

 

[racerone]

No surprise to me !!----I have a number of these 6 hp motors.-----All have new coils now.

 

[Royce Brown]

Yep both cracked !!! I'll let you all know how it turns out. Thanks So Very Much. You all are Fantastic.

Curious how difficult it was for you to loosen the flywheel nut (did you need a strap wrench?) and how hard was it to pull off the flywheel (did you need to use a harmonic puller or did it pull off by hand?).

I'm at this similar point you are with my 6HP, only firing on one cylinder so I have dirty contact or bad coil......

 

[Maxamus137]

Actually it came off quite easy. Used a strap to hold the flywheel. Then just used a long screwdriver to pry up slightly and tapping the bolt easy 1/4 turn and it came off after about 3 rounds all the way around.

 

[Chinewalker]

Interesting! I stand corrected, although I don't think I've ever seen coils cracked like that in a late 1960s OMC... But, clearly it happens!

 

[racerone]

Happens or will happen to every one of them !!

 

[oldboat1]

Maximus — think you’ve got it. Suggest you do half the magneto at a time so you have the other half for reference. May want to replace coils, points, condensers and wires at the same time, but depends on how things look to you. BTW, you can check any new assembly (check for spark) by carefully putting the flywheel on over the key, and spinning clockwise by hand. Use a spark tester like this:

 

[Maxamus137]

Thank you, I'll just what you suggest, dont wanna have to take it all apart again. You all are Great

 

[Maxamus137]

Just wanted to Thank everyone who helped me. I got the new coils in and reset the points , RUNS LIKE A CHARM. THANKS EVERYONE

 

[oldboat1]

Good boating to you, Sir!