Pressure Testing Lower Unit for Water in Gearcase . . . HELP

[PATRIOT]

1987 Nissan NS15-B
15HP
2-stroke

Attached is a pic of my lower unit gear lube which shouldn't look like thin mustard.
So, I pulled the unit . . .
1) submerged the unit in water up to the bottom of the water pump housing
2) removed the shift rod
3) applied 10-15psi compressed air to the shift rod port
Results . . . NO BUBBLES anywhere.

I'm stumped . . . any ideas on how the water is getting into the gearcase?
Have never pressure tested a lower unit so I'm not even sure this is a good method . . . it just seemed reasonable?

 

[Pappy]

Pull the water pump. Re-install the shift rod. Use the vent hole for this.
You only need soapy water for the checks, no need to submerge. Spray all seals.
After draining all oil pressurize to no more than around 10psi.
Rotate driveshaft and note the result. Wiggle it side to side a bit as well.
Shift the shift rod and wiggle side to side, again note the result.
Check the fill and drain screws for proper seals. Were they tight?
On a double seal arrangement you can hold pressure and not hold a vacuum.
Pull a vacuum on the gearcase, out of the water, and make your checks, same as above.
While out of the water if you do not have a gauge you can use soapy water for both press. and vacuum.
The bubbles will get sucked in on a vacuum leak. Get bigger with a press. leak.

 

[PATRIOT]

I'll give all that a try . . .
BTW, the water gets into the oil even when I use the muffs . . . boat on the trailer.

 

[Pappy]

Then it should either be the driveshaft or shift shaft seal(s).
You could not test the shift shaft seals with the method you were using and you could not see the driveshaft seals.
This method should tell you what is leaking.

 

[PATRIOT]

Update:
Drained rest of gearcase oil . . . re-installed shift rod . . . removed water pump . . . applied compressed air to top oil level port . . . sprayed all exposed shafts and seals with soapy water.
No bubbles . . .
Filled gearcase with new oil and installed back on motor.
Ran motor for a good 30 minutes submerged in water tank both in gear and in neutral.
Motor submerged overnight.
Tomorrow I'll drain the oil and see the results.

 

[Pappy]

You may need to pull a vacuum on the unit as well.
Back to back seals can have either one leaking.

 

[PATRIOT]

Will do.

 

[PATRIOT]

Pulled a vacuum and got same results . . . water in oil . . . held a vacuum pretty much and sucked up no soap bubbles.
Back to square one.

 

[Pappy]

Okay, at this point I can tell you that if it were in my shop I would pull the driveshaft bearing housing and change all seals. Pull the shift rod housing and change seal and o-ring there as well.
You provided a good clue in that if you are just running on a hose the unit takes in water. The two most likely culprits are those I mentioned.

 

[muddywaders]

Check end play of prop shaft and also run out(bent shaft).A propeller that is damaged and has excessive vibration will cause water intrusion.Probably the usual suspects Pappy mentioned.mw

 

[PATRIOT]

Okay, at this point I can tell you that if it were in my shop I would pull the driveshaft bearing housing and change all seals. Pull the shift rod housing and change seal and o-ring there as well.
You provided a good clue in that if you are just running on a hose the unit takes in water. The two most likely culprits are those I mentioned.

I'm leaning towards the water pump lower oil seal myself now. I just didn't want to start throwing parts at it. That seal has me puzzled because it shows no sign of leaking when I pressurize the gearcase or when I pull a vacuum. I cannot see how water under water pump pressure can make it's way to the seal though??
One last thing I'm going to try today is draining and cleaning the gearcase (not refilling), remove the oil drain plug, and run the engine (in neutral) on the fake-lake for a while and see how much water comes out.
Stay tuned.

 

[Pappy]

Okay...although I do not see upper and lower seals. Look at 26 and 27. Did you pull the lower plate off the driveshaft housing for a better visual?

 

[perchjerker]

I would just replace all the seals. And make sure the sealing surfaces on the shafts are not scored.

If one is going, the others may follow if they are all the same age

this way you have all new seals and can sleep at night

If I rebuild an engine I just replace all the seals. Not just the leaking one

similar logic applies here

 

[PATRIOT]

Okay...although I do not see upper and lower seals. Look at 26 and 27. Did you pull the lower plate off the driveshaft housing for a better visual?

So . . . today I ran her on the fake-lake, at idle, for 10 minutes (stopwatch) with an empty gearcase (lightly pre-lubed bearings) and then drained a full tablespoon of water from the lower unit. It appears the water under pressure from the water pump was somehow making its way into the gearcase. Seal kits on order . . . pressure testing didn't tell me anything useful I guess Pappy.
Had to rig a Redneck-Seal-Puller after all this.

 

[Pappy]

That is actually pretty ingenious!
We tried to help a guy out at one of our antique outboard meets with a failed driveshaft seal. None of us had anything to knock the seal out with that wouldn't damage the housing. His weekend was done as far as that engine went until he got back to a shop. That method would have worked.

 

[PATRIOT]

Mission accomplished . . . up and running!
Nissan Tohatsu out of Dallas was very helpful in going to bat for me to get my local dealer to include ALL seals and gaskets to do the lower unit with a kit that was short. I found it hard to believe the dealer would even argue. Told him I have a long memory and I'm shopping for a new $4K motor. His response "purchase the missing seals and I'll refund the price when you buy the motor" . . . . . . NOT.