oil leak 1990 Johnson 8hp

[lselmes]

Just wanted an opinion as I'm not too experienced with outboard repairs. On Sunday I replaced my lower unit gear oil, replaced my spark plugs and ran some seafoam through the carb and let her run in the tub for 20 minutes and she ran like a charm. Everything seemed great and ready for some winter blackmouth trolling. So today when I went to retrieve the motor I noticed a leak coming from the lower unit seal/gasket... any idea's what this could be or what would have caused it? And is it a simple repair or something a mechanic should do? Thanks in advance if someone can help me out.

Cheers

 

[bktheking]

Re: oil leak 1990 Johnson 8hp

That's a strange place for the oil to come out, it should be leaking out of the prop hub and onto the ground. I'm guessing that you have a bad lower crankseal as the unburnt oil should travel down the exhaust tube and shouldn't appear above the gear case. If you are mechnically able it's a matter of pulling the power head and replacing the seals (crankshaft and driveshaft) and o-ring, they are on the exhaust housing on this motor.


This is what I'd be taking a guess at.

 

[lselmes]

Re: oil leak 1990 Johnson 8hp

Thanks for the input. Any other ideas out there before I start tearing the powerhead out?

 

[kbait]

Re: oil leak 1990 Johnson 8hp

I think there's a little weep hole somewhere below where the oil is leaking that is supposed to vent the 2-stroke exhaust sludge out. If that was blocked, it could cause the gunk to leak out where it is. Try to clear out that port, and drain and inspect gear lube. If the gear lube is fine, I'm likely correct. Especially since you just sea-foamed it. Lots of gunk probably wants to escape somewhere...

 

[lselmes]

Re: oil leak 1990 Johnson 8hp

Thanks for quick reply. I'll go look for weep hole. Just one more question..... if the oil is geeting past the lower unit seal/gasket as pictured does this mean the gasket is shot as well?

 

[bktheking]

Re: oil leak 1990 Johnson 8hp

Thanks for quick reply. I'll go look for weep hole. Just one more question..... if the oil is geeting past the lower unit seal/gasket as pictured does this mean the gasket is shot as well?

There is no gasket , it's metal on metal, as I said before, oil shouldn't be coming out from there. When a 2 stroke outboard runs any unburnt oil should travel down the exhaust tube and out through the hub or the weep holes KBAIT is referring to, check them out. But from what I remember on my 9.9 (I know it's not an 8) the weep hole is lower than the mating surface of the gearcase. I'm most familiar with the 9.9s, on the bottom of the exhaust tube. I take back what I said after looking at the diagram. From what I can see the exhaust tube is very short, I think you've just loosened up some garbage in the exhaust housing and that's where it has chosen to run out. Clean it up and run the motor a few times and see if it continues. It won't hurt anything either way.

 

[lselmes]

Re: oil leak 1990 Johnson 8hp

Awesome info, very informative and very much appreciated! I'm thinking the same thing about all the crud as I had lots of chunky bits and my plugs were horrendous before blasting the carb with seafoam. In my water tank there was lots of black solid floaties and who knows where the rest of the stuff ended up. Can you give me some advice for doing a thorough cleaning to get the rest of this crud out of my system as this is all new to me. Many many thanks again!

 

[Vic.S]

Re: oil leak 1990 Johnson 8hp

Yes the inner exhaust tube only extends a short distance down inside the outer exhaust housing and the prop is not a through hub type!

Any unburnt oil does end up on the top of the gear case although there are I think some small drain holes along that horizontal joint.


It is just a metal to metal joint and if there is any corrosion or perhaps if it has been knocked and distorted a little oily gunge will leak from that joint.

lselmes

Do not strip it down to investiagte if there is nothing else apparently wrong!

Unblock any little drain holes along the line of theat joint and clean the joint up best you can when you next drop the LU to renew the pump impeller.

 

[lselmes]

Re: oil leak 1990 Johnson 8hp

Thanks Vic S. for the info. This is a great forum and you've all saved me some time and money as well as educating me on this motor. I know have a much better understanding of the inner workings of this motor as my past small 2 stroke outboards drained unburnt oil through the hub. I'm new to the Johnson to the line and will definitley be getting myself a manual so next time I can hopefully solve it myself while knowing that I also have a great forum to pick the brains of some really knowledgeable folks! For the record my 1990 8hp Johnson is a model J8RESR.

 

[Vic.S]

Re: oil leak 1990 Johnson 8hp

FWIW I have just been and looked at mine.
It is also weeping from that joint and yes there are a couple of drain holes, one either side about a centimetre or so back from the front.

may be worth checking that the long bolt that secures the gearcase at the front is tight.

 

[bktheking]

Re: oil leak 1990 Johnson 8hp

Sorry about the wrong advice bro, thought the 8 was like the 9.9 until I took a closer look at the diagram (all based on what kbait said). Go to shop.evinrude.com and go to the parts lookup, lookup your motor, you will see an exploded view of the entire motor section by section. The lower unit on that motor has the old style lower unit without the through hub exhaust, you'd think evinrude would have done away with it since through hub was 20+ years old

 

[lselmes]

Re: oil leak 1990 Johnson 8hp

I almost forgot.....is there any way for the unburnt oil to somehow make its way into the gear case and contaminate the fresh gear oil I just put in?

 

[lselmes]

bktheking

bktheking

No problem bktheking. You as well as me have learned something new today from a great forum of knowledge and caring people!

 

[Vic.S]

Re: oil leak 1990 Johnson 8hp

is there any way for the unburnt oil to somehow make its way into the gear case

Not if the seals are Ok. If they are not then water getting in will be a bigger worry than any of that gunge.

If your old oil was clear and bright when you drained it all should be well.