Johnson 1987 6hp unburned fuel

[Knotstrait]

got this motor a week a ago, it was sit for more then 5 years, the guy tried everything to start it, start fluid, change plugs, not even turn, finally he fired it up with drill, two day later I took it to the bay it started on first pull, idle good, I ran it for an hour trolling speed, after that took it home flushed it, and next day I saw the dark oil/gas leak out from lower unit connect point, (showed as picture). Both cylinders has 70 psi compression, what can I do to stop the leak? Thanks for any input!

 

[flyingscott]

I am.not sure you have a leak. It looks pretty normal to me usually happens after a lot of idling time. You may want to change your waterpump impeller and put a carb kit in there.

 

[Joe Reeves]

Does the fuel primer bulb pump up hard and holds that hardness?... Or possibly it gets hard then slowly starts to collapse if you hold pressure on it?

If it doesn't get hard or starts to collapse under pressure, suspect a flooding carburetor or/and a cracked fuel pump diaphragm.

When this leakage took place... was the engine in a tilt position with a portable tank hooked up to it?

 

[Knotstrait]

Flyingscott, thank you, yes, the guy said he was the original owner, and the motor used very little, he had never clean the carb ever, so I guess it’s time to clean it!

 

[Knotstrait]

Joe, thank you for the reply, the dark oil/gas didn’t show up till next day after I ran it, even when I drove home had it lay on the side for over 45 minutes, my car was clean. When I got home, i flushed it, put it on the stand just like showed on picture, the portable tank wasn’t connected. I didn’t see the leaking till hours later! I did ran the carb empty before I put it away!

 

[Joe Reeves]

Some of the 9.9hp and the 15hp exhaust thru prop models have been known to have excessive unburnt fuel run down the long exhaust chamber and flow out the prop... BUT... this is the first time I've ever seen anything even slightly close resembling that problem on a 6hp model. That exhaust chamber and tuning tube must be saturated with soot.

Perhaps it just needs a good long run at a high rpm to clean it out... BUT... please do pay attention to check the fuel primer bulb pressure as I suggested when you run it again.

 

[Knotstrait]

Thank you, Joe, I will pay attention to the primer bulb next time, and try to run it on a high rpm!
can the exhaust chamber and tuning tube be cleaned?

 

[Crosbyman]

by design……. when the burnt fuel goes out on the down stroke and the new fresh fuel comes in the cyl due to crankcase pressure build up from that same.. downstroke

both the exhaust ports and intake ports are open allowing some fresh fuel to exit with the exhaust (my understanding anyway)

that sends fresh gas and oil down in the exhaust cavity and probably loosening up years of black crud (soot as JR mentioned)


run the engine for a while and things should ..dissolve it self :joyous:

mean time keep a bucket of cat litter sand under that keel or get cheap diapers at the Dollar store for your new baby !

 

[Joe Reeves]

Thank you, Joe, I will pay attention to the primer bulb next time, and try to run it on a high rpm! can the exhaust chamber and tuning tube be cleaned?

To clean manually, a lot would need to be dismantled. You do not want to get involved in that. I assume that the previous owner was using quite a rich mixture (oil) or doing an excessive bit of trolling... OR... and most likely using the engine on some craft whereas the propeller was not a match for the boat, causing the engine NOT to reach its proper rpms at full throttle.

As "Crosbyman" states...that soot should blow out of there eventually.

 

[Knotstrait]

Thank you guys, I am happy that it’s not a big issue! Does the psi both at 70 sounds right? I used it for my 9 foot hard bottom dinghy, 2 people and a dog about 300 lb, we couldn’t get it on plane, a little dispoint!

 

[Silvertip]

You are asking a 6hp engine to do 10 HP worth of work.

 

[Crosbyman]

nice…. trolling motor not a racing engine !!


70 psi… not what you would call a tight engine but get it going and run some decarb product (merc power tune… BRP carbon guard etc...) in it and it will help revive things a bit.

 

[Knotstrait]

Thanks a lot! Will try the carbon guard next time!

 

[tomhath]

No offense intended, but have you checked that the bolts holding the lower unit on are tight? Someone might have changed the impeller and left them loose.