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Hello,
I have a 1986 Johnson 90 on my Montauk. Rinsed the motor and put it in the garage after a day of fishing. Next morning there was a small pool of black oil on the floor just below the lower unit. What is the prognosis? Do you think the seals went south?
When did you last change the lower unit oil? IS it milky white now? Oil on the floor is black so lower unit oil is either burnt or old or other........ So may not be lower unit oil. My 84 Johnson 90 will leave black oil on the floor the first couple trips after de winterizing and de carb. This oil comes out through the prop is kind of thick.
Did you have fishing line wrapped on the prop lately? Hit anything?
Have you been out many times recently and just now this is happening?
BTW I had all my seals changed because I wrapped line on the prop and blew the seal.
Pete
remove the prop and check that seal, if you run over a fishing line it gets wraped around the shaft and can destry the seal causing it to leak, if thats not it then it is the unit seal
It is likely that this is carbon, not oil...it is coming from the exhaust hub, and it means that you are either running very rich or have a lot of carbon build-up in your motor.
Of course, we first need to confirm that it is NOT the lower unit, which is easy: Go into the kitchen. Grab one of those twisty-ties that your wife keeps in the drawer for when you don't put it back on the loaf of bread (we know - like all guys, you spin the loaf and tuck the bag underneath!).
Remove the vent screw on the lower unit (the upper screw) and put the twisty tie in there...fish around and remove it. What does the oil look like?
Is it jet black? If so, you either haven't changed the lower unit oil in awhile, or you have a problem. If the former, change the lower unit oil. It should be mostly an amber color (if traditional oil) or blue/green (synthetic oil).
Is it Milky? If so, you have a problem with water getting in there and you need to address that as outlined above.
If neither - then it is most likely that you have carbon build-up, or are running very rich...or perhaps you are "overpropped" and the engine is lugging. Here's the quickest way to tell that you have an "exhaust problem" rather than a lower unit problem: Take a clean finger and run it around the inside hub of the prop. If it comes out with a thick coat of soot, your engine exhaust is too rich - full of carbon. It can be a lugging problem (overpropped - what is your WOT RPM?) or it can be simply that your engine has a lot of carbon built up and is blowing it out the exhaust.
Here is my recommended way to decarbon a carburated motor:
Disconnect the main fuel tank. Connect a small (perhaps 3 gallon) auxilliary tank and mix up a brew of clean fuel with a very strong dose of Seafoam (in a can, not the spray). Next, tilt the engine and remove the spark plugs. Pour in another can of Seafoam in all of the cylinders, turning the flywheel by hand. Let the motor sit for 2-3 hours.
Return to the boat and tilt the motor down and start the engine. If the engine "races", use the kill switch to kill the engine and start it again. It will smoke quite a bit. Take the boat out for a ride - running the motor at varying throttle settings and making sure to clean the whole auxilliary tank.
Reconnect the main tank. Add Carbon Guard additive to every tank (if the boat is used only sporadically) or every other tank if used often.
Wipe out the prop hub and do the finger test again. If it still is sooty, consult your mechanic.
