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Milky gearcase oil

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sailortom

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i bought a 1982 johnson 4hp mo

i bought a 1982 johnson 4hp model j4brcnr. it runs fine but the gearcase oil always turns milky. this is my first outboard and i assume water is getting in the gearcase. the drainplug has a washer on it but the screw above it does not and the parts schematic i found online does not show a washer for this other screw. is there another place to look for water intrusion? how damaging might this be as long as i change the oil often?
 
"a pressure test,will most lik

"a pressure test,will most likely,find ur prob..pull lower unit,rig a small hand pump,and a fitting,or such,to pressurize slightly,the lower unit,and look for bubbles,when submerged in a small tank,of clean wtr."
 
"Puzzled by the apparent lack

"Puzzled by the apparent lack of washer on the upper screw! Different to the drain screw though. Mostly they are the same and have identical washers

I think I'd make sure that is properly sealed and fit a new washer on the drain screw and try again.

Most likely place for water ingress is via damaged propshaft seals (Easily damaged by fishing line.) but as Jwb says a pressure test should show where it is leaking. Only snag is that the seals are double (Two the same back to back so that one keeps oil in while the other keeps water out) and it is possible for it to hold air in but still allow water in.

If you do not know the age of the pump impeller or if it is more than just a few years old it is worth stripping it down, replacing the prop shaft seals and housing O ring and the driveshaft seals together with the pump impeller. You should then be able to run without any worries.

If you are running in fresh water then its not too unreasonable to change the oil frequently until convenient to sort things out but if its salt water then the sooner you sort it the better."
 
Sure enough ... the diagram do

Sure enough ... the diagram doesn't show a washer on the top vent screw ... never seen that before on any other motor. I wonder if it's a mistake in the factory parts diagram?
 
There is a separate screw on m

There is a separate screw on most older ones that secures the shift pivot linkage and is not the drain port. I am not familiar with your motor but something to maybe be aware of.
 
"I found the same screw on ven

"I found the same screw on vent missing a gasket and had milky oil. before i replace it i wondered if i should blow air through to get last bit of emulsified oil from lower unit, or use solvent like kero, or both. maybe no need just let drain?"
 
"Let it drain, Fill it up and

"Let it drain, Fill it up and then flush it again use only gear oil. Be sure to check it again after running on the lake since it very well could be additional leaks like your shift rod seal etc.
I had the same problem and thought it was the filler plug also, found out it was the shift rod seal easy fix also .."
 
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