Is water getting in my gearcase?

[MarshMarlowe]

1997 Yamaha C90TLRV

About two months ago, as I was prepping the boat, I noticed the vent screw on the gearcase looked wet with oil. I checked it, and it was loose. I decided I should drain the gearcase and what came out looked like pancake batter. No question it was full of water. I figured it was probably just leaking at the loose vent screw, so I refilled it and drained it a few times in an effort to get all of the moisture out. I then had the gearcase pressure tested, and it held 15psi for 20 minutes before we stopped the test. I did not have it vacuum tested. I refilled it with fresh Yamalube gear oil once more along with new screw gaskets. I ran the boat twice since then, and let it sit about a week. Drained yesterday, and this is what it looks like-



Let it sit 24 hours, and it looks like this now -



Does it look like water is in the oil?

[TownsendsFJR1300]

YES, definitely..

When you checked with pressure, was the gear case empty of oil?

[MarshMarlowe]

YES, definitely..

When you checked with pressure, was the gear case empty of oil?

Yes it was empty

[TownsendsFJR1300]

Odd that it held pressure but that oil should look just like it went in.

Perhaps when running, under load, its then picking up water/leaking.


Definitely needs further investigation...

[MarshMarlowe]

Yeah it didn't sit well with me... Perhaps I will put together a vacuum test

[TownsendsFJR1300]

On the parts fisch:
1997 C90TLRV Yamaha Outboard LOWER CASING DRIVE 1 Diagram and Parts

There are two seals under the water pump impeller, part #27.

My dealer recommending changing them out (just over time, no leaks).
Sure enough, one of the seals, the SS spring that wraps around the seal for a tight seal, was broke...

You may want to peek under there..

When he checked (forgot if it was pressure or vacuum) he turned BOTH shafts (prop and drive) while watching his gauge. Should one of those be bent/loose, etc, rotating them should show a leak

[robert graham]

Remove prop and check for fishing line around/under prop shaft seal....

[MarshMarlowe]

Remove prop and check for fishing line around/under prop shaft seal....

I've checked, there is no line

On the parts fisch:
1997 C90TLRV Yamaha Outboard LOWER CASING DRIVE 1 Diagram and Parts

There are two seals under the water pump impeller, part #27.

My dealer recommending changing them out (just over time, no leaks).
Sure enough, one of the seals, the SS spring that wraps around the seal for a tight seal, was broke...

You may want to peek under there..

When he checked (forgot if it was pressure or vacuum) he turned BOTH shafts (prop and drive) while watching his gauge. Should one of those be bent/loose, etc, rotating them should show a leak

That's good info. I changed the water pump not long ago, but I'm a little foggy on what was involved. Would inspecting those lower seals require me to replace gaskets on the pump baseplate upon reassembly?

[TownsendsFJR1300]

Would inspecting those lower seals require me to replace gaskets on the pump baseplate upon reassembly?

Per my shop manual(F150), yes. The top seal spring(actually both of them) should be facing up and the SS spring should be there.

Should you have to replace them, MEASURE HOW DEEP THEY ARE, as there is no factory # for the depth but to put them back as deep as the old ones...

Do you have a shop manual?