1986 Johnson 6 HP - Gear Case Gasket Replacement

Refer to the motor diagram in the attached link for the numbers listed by part names.

I picked up a 1986 Johnson 6HP this week and have been able to get it running. I've got it hooked up to the motor flusher and when it's running, it leaks oil and water around joint where the gearcase (#61) meets the extension (#68). I've never taken a the gearcase off but it looks like there are only a few bolts. I'm thinking that it just need to replace the gearcase cover gasket (#14). I'm assuming that I should drain the lower unit oil, then remove the gearcase and replace the gasket then put it all back together and fill with ouil again. Is there anything else that I need to do? Based on the problem description, does my diagnosis even seem right? This is my first go at this, so any help would be great.

Also, when it's running wide open it runs fine, but when I ease off the throttle it won't idle and just dies. Any suggestions on tuning it up? Every time I start messing with a carb, I seem to make it worse.

Thanks in advance!!


https://www.marineengine.com/parts/...=J6RCDE&manufacturer=Johnson&section=Gearcase

If the oily discharge smells like a combination of oil/fuel then it is unburnt fuel, which will happen with a 2 cycle motor. There is usually a weep or drainage area to prevent the built up of old unburnt oil/fuel. Your best bet is to check your lower unit and look at the condition of the oil. If it is milky or you have water coming out of the lower unit then you have lower unit leak, that may be due to bad seals. If you smell the lower unit oil and the darkish grey/brown unburnt fuel/oil seeping they should have two distinct smells. Again, your best bet is to check your lower unit and look at the condition of the oil.


As for your running condition, your slow idle maybe out of adjustment. You run fine wide open but idle very poor or kill at lower speeds. Before tearing into your carburetor to clean and install a new carb kit, try resting your slow idle needle.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Turning in means to turn the needle clock wise.
Turning out means to turn the needle counter clock wise.


Initial setting is: Slow speed needle = seat gently(turn in), then open 1-1/2 turns(counter clock wise).

Start engine and set the rpms (adjust the throttle) to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds (about 8 to 10seconds) for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Click to expand...

Hope this helps you out!