Logo
FULL SITE MENU

1984 Johnson 90 hp V4 2 stroke Fuel Oil leak from under upper exhaust housing

M

MitchB

New member
I have seen quite a few threads related to this problem. I have a fuel oil mix leaking out from under the upper exhaust housing. Engine seems to be running good and starts fine. The leak is significant enough to be visible in the water. Ironically, the fuel recirculating hoses were leaking and not installed correctly, now that they are routed right and connected to the nipple to lubricate the main shaft bearing the leaking out the exhaust directly below the engine seems to be worse. I realize that this will take some tearing into to isolate but any insight on what appears to be a common problem on older two strokes. Exhaust related gaskets or Main shaft seal maybe?

Thanks, MitchB
 
is this motor new to you?why were the hoses routed wrong?is this ''leak'' a leak or is is unburned fuel coming out of the exhaust?have you run the boat for a good run to get rid of any residual left from the hose swap?is the fuel you are seeing on the water little droplets coming out of the exhaust or a puddle like a leak?
 
Motor is new to me and of unknown history. It has definitely been tinkered with, not surprising being 30 years old so don't know why hoses were wrong but confident they are right now. I don't know if there is unburned fuel getting blown out the exhaust although I wouldn't be surprised if it was. The leaking I am seeing comes from underneath the exhaust housing covers right under the engine. I guess it could be called more puddle like as a film of fuel/oil accumulates behind the boat when stopped. Significant and embarrassing at the boat dock. I know the underlying causes could be many and will begin the trouble shooting tomorrow. Dreading having to pull the powerhead. Like I mentioned I have seen some threads on this but havn't noticed any definitive fixes. There is a little that seems to get on the bottom portion of the cowling in the rear but my suspicion is that most of it comes from where I cannot see. Any trouble shooting tips or things to inspect before I consider ripping it apart. Thanks for the reply.
 
Thanks papyson for the link to that thread, sounds like what I have going on. It was a very helpful read. After checking the Cylinder compressions and a couple of other things I plan to try and replace the gasket from exhaust adapter to powerhead, inner gasket below the exhaust adapter and hopefully the lower seal on the crankshaft. I have a good amount of wrenching experience but admittedly I am new to the outboard world...which brings me to another question which a new thread may be needed. I am using the model specific OMC service manual as well as an aftermarket Seloc manual. They both instruct to remove many things off the powerhead to remove it. i.e. - carbs, starter and solenoid, by pass covers and much more that seems uneeded just to lift it of the exhaust adapter, maybe naive here. Obviously the connections such as controls, shift rod, some electrical and so on need to be cleared. I get it in order to further disassemble the powerhead but to just free it enough to lift do you really have to strip it of so much?
 
sorry for delay....been at my camp for a few days but even tho i have a computer there i was busy...i use those books as a checkpoint on tear down and not as an absolute guide...
 
The "U" shaped plastic cover under the hood pan is secured with 6 bolts, remove it for a better view if you haven't already done so.
 
Back
Top