9.8 Gear oil leaking

[Just a grease monkey]

I have a 9.8 that sat for some years. I believe it a 1979 model. When i went to fill the lower unit with oil, first of all, i found it was empty. I then started to fill from bottom as book says to do with top vent screw removed. Oil almost immediately came out at I believe the water pickup down below. Only other thing there is the stud which is a pretty good fit and I can't see it coming out that fast if there was a clearance problem with stud. I'm now confused about how this all even is supposed to work.
It appears the oil is pumped into the water pump housing and goes up the tube and out the vent, I put some oil in top vent hole to see where it came out and its coming down through the tube to the water pump.
So i'm confused as to how this is supposed to work and what could be problem.

 

[Texasmark]

Re: 9.8 Gear oil leaking

The LU gearbox has 3 exits besides the fill/drain screws: The shift shaft seal which is about an inch below the top of the shift shaft; the drive shaft seals which are under the lower plate of the water pump; the prop shaft seals which are at the rear of the bearing retainer immediately in front of where the prop mounts.

The process to fill from the bottom is to ensure that you get the chamber full. Pushing oil up from the bottom pushes trapped air out. Installing the vent screw first sets up a vacuum so that when you remove the filler tube from the new lube, little oil will be lost in getting the fill screw installed and secured.

Since you said your engine sat for awhile, you could have dirty oil in the LU in which the impurities settled to the bottom and caked up. That would explain why removing the drain screw with no oil coming out gave you the impression the chamber was empty and when you added oil it immediately came out the vent.

So I'd remove both screws and get a wire and clean out the drain screw area letting all the existing oil drain out. Then fill with fresh. Run the engine for awhile, say a couple of hours as you normally would and then check the oil. If full and no yellowing (water intrusion) you are good to go.

Mark