lame 68 6hp Johnson

[geoffwga1]

I am currently reviving a 1968 6hp johnson. Mod# CD 25r.
Have done compression check,70/75 each cylinder ,have nice fat sparks on tester,and plenty of fuel getting through.
Starts and runs fine but only on 1 cylinder(bottom) My next thought is a reed problem and thereby lies the rub. What tool do I need to remove the reed cover plate screws? the top ones are OK but there is no room to get at the bottom ones with any ordinary screwdriver.I would happily remove the power head to do it but the manual says first remove reed cover plate,so we have chickens and eggs.Any ideas or suggestions would be more than welcome.Thanks in advance guys.

Geoff.

 

[oldcatamount]

Re: lame 68 6hp Johnson

If you have "plenty of fuel getting through", then you don't have a reed problem. How do you know it's running only on one cylinder?

 

[geoffwga1]

Re: lame 68 6hp Johnson

I know fuel is getting through because it's running fine on the 1 cylinder,and I know which one by the simple expedient of disconnecting the plug leads in turn.Disconnect bottom.Engine stops.Disconnect top.No change.If you don't think it's a reed problem that's fine,I hope it's not but I'm open to suggestions as to what it could be. Plugs are new and gapped correctly.
Geoff.

 

[oldcatamount]

Re: lame 68 6hp Johnson

After running the motor, are there signs of fuel on the top plug? Also look closely at the top plug for signs of water.

 

[lindy46]

Re: lame 68 6hp Johnson

Sounds like a bad coil to me. It may spark ok in a test tank at idle, but be cutting out once things warm up.

 

[boobie]

Re: lame 68 6hp Johnson

Are you just running it at idle or WOT in a barrel or on the water??

 

[geoffwga1]

Re: lame 68 6hp Johnson

I amrunning it in my test tank.Out of gear it revs quite well as can be expected in gear however about 1500rpm maximum.tomorrow I will tryna different coil to see if that makes a difference.
Geoff.

 

[kbait]

Re: lame 68 6hp Johnson

You may want to change that condenser, or swap 'em to see if the no-fire switches to the other cylinder.

 

[geoffwga1]

Re: lame 68 6hp Johnson

Good Idea Kbait,I'll try that tomorrow,I didn't get a chance to do anything today,I was on honeydoo duties.
Oldcatamount,no signs of water,both plugs a bit wet but top one more so.
Geoffwga1

 

[Monte1961]

Re: lame 68 6hp Johnson

One of the most tell tail signs of bad coil/s is discoloration and or cracks! Good luck and post yer results!

 

[Swell]

Re: lame 68 6hp Johnson

Just to add my bit - I'd narrow it down as far as possible before pulling the reed plate. I recently did a full-ish overhaul on a 1968 Johnson 6HP and all associated gaskets fell apart when I pulled the reed plate - easy enough to replace but best avoided if possible. From memory I'd imagine it would be almost impossible to remove the reed plate without removing the power head. I seem to remember they are slot headed bolts which are a bit of a nightmare compared with hex heads.

 

[geoffwga1]

Re: lame 68 6hp Johnson

I pulled the reed plate anyway just to make sure but they were all OK so we're back to the top end again.I still have to check the coils when I get back to it.You are right about the reed plate screws.I finally got them out with a flexible screwdriver extension(courtesy Harbour Fright).When I put it back I exchanged the screws for allen screws,no trouble at all then.
Cheers Geoffwga1

 

[Swell]

Re: lame 68 6hp Johnson

One other thing to check is the HT wires from the coils to the spark plugs. They are routed close to the powerhead. If they're old and degraded the top one might be arcing off the powerhead which would mean a weak spark or no spark by the time it reaches the plug. Should be possible to see the arcing if its happening with the lights off. You could also try a temporary re-route of the cable away from the powerhead to see if that improves things.

 

[DJ]

Re: lame 68 6hp Johnson

"Reeds" are NOT the problem. You have ONE set feeding both cylinders.

You are losing spark-somewhere-not uncommon.

You are due for a full tune-Coils, points/condenser/plugs (CHAMPION-ONLY!!!!).

Nice little engine, do that stuff and it will run for another fifty years.