Water in 280 dp lower unit but pressure test is good?

[DRCrowe]

I have a 280 dp that I was servicing and found water and milky oil when I drained it.
I decided to pressure test and see if I could find the failing seal but didn't see any bubbles? I've left the pressure pump connected to the outdrive and it has been at 10 PSI and hasn't moved for over an hour. I spun the prop shafts by hand but nothing changed. I'll probably change the prop shaft seals on principal. Any other seals I should worry about? what about the shifter fork shaft? Thanks

 

[bruceb58]

Do you replace the seals around your drain plugs every time?

Also, I would also do a vacuum test.

 

[Scott Danforth]

Did you do a vacuum test as well?

 

[DRCrowe]

Hi Scott and Bruce,
Thanks for taking the time to respond! Looks like I should have waited to post until I did the vacuum test as you both mention. I wanted to see if the pressure test held overnight which it did. Apparently the oil seals aren't the issue.
This morning I performed a vacuum test. I started at 7 inHg as the manual suggests and it held fine for 20 minutes. I then tried increasing the vacuum to 14 inHg per the manual but had trouble getting past 10 inHg. I got to 11 and stopped and noticed the vacuum drop and settle in around 8. I tried packing grease around both prop shaft seals (dp unit) I packed the small shaft first then retested and then the larger shaft and retested with no change, at 11 inHg it would leak down to around 7 inHg where it holds pretty steady (at least it has for the last 45 min.)
I'm starting to question the shift fork seal? There seems to be oil covering the mechanism. I will attach a pic of the drive shafts that I packed with grease and the oily shifter.
Thanks again for your help.

 

[bruceb58]

Hi Scott and Bruce,
Thanks for taking the time to respond! Looks like I should have waited to post until I did the vacuum test as you both mention. I wanted to see if the pressure test held overnight which it did. Apparently the oil seals aren't the issue.
This morning I performed a vacuum test. I started at 7 inHg as the manual suggests and it held fine for 20 minutes. I then tried increasing the vacuum to 14 inHg per the manual but had trouble getting past 10 inHg. I got to 11 and stopped and noticed the vacuum drop and settle in around 8. I tried packing grease around both prop shaft seals (dp unit) I packed the small shaft first then retested and then the larger shaft and retested with no change, at 11 inHg it would leak down to around 7 inHg where it holds pretty steady (at least it has for the last 45 min.)
I'm starting to question the shift fork seal? There seems to be oil covering the mechanism. I will attach a pic of the drive shafts that I packed with grease and the oily shifter.
Thanks again for your help.

That is a common leak area.

 

[Scott Danforth]

if you ever had water in the bellows, the front seal is a suspect area
the shift assembly is another leak point
the dipstick and service port on the top are another leak area
the lower unit has a few leak points.

are you turning the shafts and shifting while doing the pressure test and vacuum test?

 

[DRCrowe]

Hi Scott,
if you ever had water in the bellows, the front seal is a suspect area - I had a bad oil leak in the front seal last year. Lots of oil in the bellows but no water. I replaced the front seal and the sealing ring (which had a visual wear pattern and I didn't want it to eat another seal!) I am going to pull the upper bellows to see what it looks like. fingers crossed!
the shift assembly is another leak point - I just ordered OEM seals for the shift assembly and will replace. Lots of oil all around this thing. Probably the leader in the clubhouse for the leak!
the dipstick and service port on the top are another leak area - I just ordered Sierra o rings for drain, dipstick and filler screw. I couldn't find any OEM o rings that I could get in a reasonable amout of time. Is this a mistake?
the lower unit has a few leak points.

are you turning the shafts and shifting while doing the pressure test and vacuum test? Yes, many times with the pressure test with no change in pressure. It held at 10 PSI overnight. I did turn the shafts on vacuum test, but not after I packed them with grease. It was still leaking.

Thanks again for taking time to help me troubleshoot. I've been lurking and reading your posts for a long time! I re-powered last year with a SBC from Michigan Motorz based on your suggestion. Really happy with how it turned out!!

 

[kenny nunez]

To reseal the shift seal you will need a good pin punch to remove the small roll pin.

 

[DRCrowe]

Thanks for the heads up Ken,
I have a couple, but might need to get a smaller one based on the pics in the manual!

 

[QBhoy]

Famous for the drain plug, dip stick seals leaking. Often they can get nipped when tightening them back up. But generally just a bad design. I used to put silicone over the plugs after each oil change. Never had an issue after. Many others now do the same.

 

[DRCrowe]

Thanks for the tip QBoy! Anything to help keep water out!

 

[DRCrowe]

Update (and quick question)
I replaced the shift seal and installed new o rings on the gear box, drain plug, dipstick and vent screw on top. Reassembled and performed vacuum test to 14 inHg per the manual and it held steady this time! One quick question, I was going to pull the gearbox back off to put the first 2 quarts in the lower unit. Should I replace the new gearbox o ring since I torqued it down for the vacuum test or can I reuse it since it was new?
Thanks for the help and support!

 

[captmello]

orings are typically single use items. using a common lower unit fill pump is the way to fill the outdrive with lube.

 

[Scott Danforth]

Update (and quick question)
I replaced the shift seal and installed new o rings on the gear box, drain plug, dipstick and vent screw on top. Reassembled and performed vacuum test to 14 inHg per the manual and it held steady this time! One quick question, I was going to pull the gearbox back off to put the first 2 quarts in the lower unit. Should I replace the new gearbox o ring since I torqued it down for the vacuum test or can I reuse it since it was new?
Thanks for the help and support!

fill from the fill port on the transmission

 

[DRCrowe]

Thanks guys! I used the fill port on top. Took soooo long!

 

[Scott Danforth]

Thanks guys! I used the fill port on top. Took soooo long!

it does. and when filling under my swim platform, I usually mash my head into the swim ladder about 3-4 times.

 

[DRCrowe]

YES Scott, me too! Thanks again for the support! Getting close for another amazing season on the water. Bottom paint next!