losing lower unit oil

[south end]

I have a 79 johnson 15. I have filled my lower unit then ran the thing in a barrel of water. I lose most of the oil on top of the water but there is not a trace of water in the oil. how can this happen? I replaced prop seals and shaft seals too.

 

[Texasmark]

Your tank is a fixed volume of water. Running your engine adds a varying amount of operational residue to this limited volume. Your oil is added to your fuel and fuel, an oil byproduct, are consumed and dumped into the tank along with the appropriate volume of air. All the mixture didn't get burned in the combustion chamber. Besides, on water, oil spreads to the height of the molecule......which are very small...probably billions of oil molecules in a teaspoon of oil. I saw a demonstration once where a guy had a pond of like 100' in diameter. Took one teaspoon of oil, poured it out on the pond and eventually (time unknown) the entire surface of the pond was covered.
I feed catfish in my pond at my farm. The feed contains animal protein and fats.....oil. In no time at all, an oil slick forms around where I am tossing out the feed. Unless something tells you differently, don't worry about it.

 

[racerone]

Not sure why the basic operation / lubrication of 2 strokes is not well understood.------When piston nears bottom of the cylinder the intake ports open.----They open just after the exhaust ports.----The incoming pressurized charge of air / oil / fuel then enters the cylinder to scavenge / clean out the cylinder.-----But some of the fresh charge also escapes.------This is what you see in your tank.----And you replaced the shift rod o-ring too I hope.

 

[roscoe]

I have a 79 johnson 15. I have filled my lower unit then ran the thing in a barrel of water. I lose most of the oil on top of the water but there is not a trace of water in the oil. how can this happen? I replaced prop seals and shaft seals too.

Are you saying the lower unit is emptying the oil and filling with air ?

 

[south end]

Are you saying the lower unit is emptying the oil and filling with air ?

yep lower unit oil escapes but the oil still in lower unit is just oil, no water

 

[QBhoy]

Or it’s 2 stroke oil out the exhaust, If you haven’t lost any gear oil.

 

[south end]

Or it’s 2 stroke oil out the exhaust, If you haven’t lost any gear oil.

Yes the gear oil empties. Capacity is about 8-10 ounces. I have topped it off and run motor in a barrel for an hour. A lot (LOT) of clabbered oil floats on top of water. Then I drained the gear oil from the gearcase. It had about 6 ounces still in the case and the oil I drained was clean. No trace of water in the remaining oil

 

[south end]

Not sure why the basic operation / lubrication of 2 strokes is not well understood.------When piston nears bottom of the cylinder the intake ports open.----They open just after the exhaust ports.----The incoming pressurized charge of air / oil / fuel then enters the cylinder to scavenge / clean out the cylinder.-----But some of the fresh charge also escapes.------This is what you see in your tank.----And you replaced the shift rod o-ring too I hope.

Sadly i did not. I just ordered a seal kit. I intend to replace all the seals and o rings again. Ive triple checked my part numbers and I have the right seals in place. I hope the shift rod seal is the problem, Im just really curious why water doesnt mix with the oil in the gearcase

 

[racerone]

Those seals last about 20 years or so.------Pressure test this lower unit to find leaks if you have any.----Why would you not replace the shift rod o-ring ?----A simple part of the job !----And how do you fill your gearcase.---From bottom to the top ?

 

[south end]

Those seals last about 20 years or so.------Pressure test this lower unit to find leaks if you have any.----Why would you not replace the shift rod o-ring ?----A simple part of the job !----And how do you fill your gearcase.---From bottom to the top ?

Did not know how to get to the shift rod seal but I do now. I fill from the bottom with a small hand pump that screws onto the oil bottle. When oil starts out of the top hole I put both plugs back in

 

[JimS123]

Sounds like the lower unit was not completely full in the first place.

 

[south end]

Sounds like the lower unit was not completely full in the first place.

I filled it from the bottom hole with a hand pump. Oil came out the top hole and i replaced top plug first then lower plug

 

[south end]

Those seals last about 20 years or so.------Pressure test this lower unit to find leaks if you have any.----Why would you not replace the shift rod o-ring ?----A simple part of the job !----And how do you fill your gearcase.---From bottom to the top ?

Did not know how to access that seal and wasnt a member of boatingforums

 

[racerone]

Shift rod o-ring is a major leak point if it is 40 years old.----Easy to replace that o-ring I say.

 

[Texasmark]

Did not know how to access that seal and wasnt a member of boatingforums

I did it once years ago. Recalling, dropped the LU and using a hook type tool, dug it out....as stated a quick fix. Sometimes drilling a hole in the metal part of a seal and using an appropriately sized sheet metal screw will give you something to grasp to remove shaft seals without having to dismantle anything.

I will caution here in that the shift shaft stub sticking up out of the LU has to be held in place while removing the seal....just incase it wants to move up with it. That shaft is splined on the bottom, just like on the top, and is just stuck in the shifting Cam Follower plate that sets the position of your shifting Clutch Dog mounted on the prop shaft. You don't want it coming out of that CF plate.........

 

[racerone]

Texas man-----You are totally wrong on the replacement of the shift rod 0-ring on this motor.

 

[south end]

Texas man-----You are totally wrong on the replacement of the shift rod 0-ring on this motor.

how would u do it Racerone? Leeroys had a chapter about this but I havent read it yet. I will read it when my seal kit comes in the mail

 

[racerone]

Take lower unit apart use 1/4" threaded rod.---Use 1/4 nut with corners rounded off and pull the bushing out.------Or run a 5/16 -NC tap in there and pull the bushing out with 5/16 threaded rod.