On a regular old-fashioned oil seal, one side is metal, and the other side is rubber. Does it matter which side goes towards the oil if the shaft is rotating (i.e. not moving axially)? I have this little machine which has 2 seals. One has the metal on the outside (which is the way I've always seen them) but the other, on the main crankshaft, has the metal on the inside. This could have been an assembly error, but maybe it just doesn't matter?
Grant Erwin
Single lip seals can be used to retain fluid or exclude dirt. When the metal is on the outside of the gearbox, the seal retains fluid When the metal is on the inside of the gearbox, the seal excludes dirt.
I just finished rebuilding a lower unit for a boat motor that used 2 single lip seals back to back. The inner seal kept the fluid in while the outside seal kept the water out of the case.
Nate
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Just curious, were there any provisions to keep the outer seal lubricated or were the seals identical? I'd think the outer seal would eventually wear out otherwise and in fairly short order.
Stan
Any lower unit I have rebuilt uses back to back, as said before one keeps the oil in its place and the other keeps the water in its place. Lower units last a long time if the seals don't fail.
The seals were identical, just reversed in orientation. There is no provision for oil lubrication, but they do run in water whenever the motor is running.
Nate
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