Yamaha 30d upper oil seals or something else ?

[gvp90000]

Dear friends,
When I removed the gear oil from my Yamaha 30 DEO 2-stroke engine it was milky ... so I've made a pressure test and I saw a lot of bubbles coming out from the point shown in the photo attached.

Is this leakage of air coming from the upper seals or I must check something else ?

30DEO
6J8K - L - 1003853
2 stroke

Thank you,
Bill

[walleye1]

Did you pull the gear case and impeller housing and check there around the drive shaft seals? Did you pull the prop and check for fishing
line? If you get fishing line around the prop shaft, it will hold the seals open to let water in and blow the gear lube out around the drive shaft.
I would reseal it complete.

[gvp90000]

I removed the lower unit and put it in a can of water to see the leakage.
I removed the prop. Around the prop shaft there is no fishing line and no leakage.
The impeller housing was on the lower unit during the test.

[fairdeal]

of course the water intakes communicate with the underside of the water pump -
exactly where the driveshaft seals are located.
So it makes perfect sense that with the waterpump assembly installed
air applied to the gearcase /leaking from the upper seals
could exit via the water intake.

If you remove the water pump and its lower plate,
you can see the driveshaft seals and confirm that is the leak
You have to do that anyway to replace them.

[fairdeal]

driveshaft seal under water pump



leaking under pressure with a little soapy water applied

[gvp90000]

Thank you very much.
I've never disassembled the pieces underneath the impeller but I think it's easy to do it ...
I have the lower unit gasket kit so i'll try it tomorrow for the first time ...

[zenoahphobic]

Be careful when pressure testing, only a couple of PSI. Looks like you have blown the seal out.

When taking out the seal atleast inspect the bearing underneath. Likely is rusted and needs replacing, you can slowly turn the shaft to detect resistance and roughness. Depending what you find, you may need to overhaul the lower unit, replacing all the seals and bearings.

Whops just realised the pictures are not GPV90000s unit?

[walleye1]

I was told in school 12psi for a few minns, I like 10 minns.

[TownsendsFJR1300]

Fairdeals first picture of the seal. If you look closely, there's a tiny stainless steel tension spring around the seal. That helps keep tension on the shaft.

They are known to fail, (go away), especially with salt water use.

I assume your pressure testing with NO OIL in the lower unit, correct?

[zenoahphobic]

Fairdeals first picture of the seal. If you look closely, there's a tiny stainless steel tension spring around the seal. That helps keep tension on the shaft.

They are known to fail, (go away), especially with salt water use.

I assume your pressure testing with NO OIL in the lower unit, correct?

The pressure testing is really just an indicator that water may get in. Oil is far denser than water and may not pass where water can, however it is usually the first indication that the seals aren't holding oil.

Air on the other hand, is thinner than water and oil and would find its way easier around a seal. The pressure test really should be done with full oil, as it can only show an oil leak at the propellor shaft, and air out past the driveshaft and gear shift shaft. Water would tend to get in through contraction when the motor is shutdown in water.

Pressure testing should be done relative to the direction of the seals, and sometimes they are in both direction. It is impractical to place a lower unit in a pressure cylinder and to measure a leak in the inside. As the worry is water getting in, rather than oil getting out, a vacuum test is what makes more sense.

[pstephens46]

I don’t know where the seals go in both directions in regards to these lower units. Lots of people seem to think vacuum testing should be done. No one seems to know the specs for such a test. So if a lower holds 10psi for 10 minutes but quickly fails a vacuum test, what should be done? Scrap it?

[TownsendsFJR1300]

The pressure testing is really just an indicator that water may get in. Oil is far denser than water and may not pass where water can, however it is usually the first indication that the seals aren't holding oil.

Air on the other hand, is thinner than water and oil and would find its way easier around a seal. The pressure test really should be done with full oil, as it can only show an oil leak at the propellor shaft, and air out past the driveshaft and gear shift shaft. Water would tend to get in through contraction when the motor is shutdown in water.

Pressure testing should be done relative to the direction of the seals, and sometimes they are in both direction. It is impractical to place a lower unit in a pressure cylinder and to measure a leak in the inside. As the worry is water getting in, rather than oil getting out, a vacuum test is what makes more sense.

I simply posted the lower unit needs to be empty of oil when pressure testing..

Oil in the LU is going to help seal up the LU seals as it is 90wt (or so). We're talking ONLY 10 PSI for 10 seconds.

BTW, years ago, (before I found this forum), the shop I used recommended checking the drive shaft seals on my motor(due to the age). I had just (not a week before) changed the LU.

The WP wear plate was removed, the small SS spring on the upper seal gone (I didn't have ANY water intrusion).

The Master Tech drained the oil, replaced both seals and I watched as he pressure tested (rotated the driveshaft at the same time), which passed.

[TownsendsFJR1300]

I don’t know where the seals go in both directions in regards to these lower units. Lots of people seem to think vacuum testing should be done. No one seems to know the specs for such a test. So if a lower holds 10psi for 10 minutes but quickly fails a vacuum test, what should be done? Scrap it?

I don't know why you would test the lower unit differently than what Yamaha calls for... Pressure testing.

Of course, without any dis-assembly (except draining oil), you can test the integrity of the LU with just the pressure test.

If it fails, you know it needs to be pulled and further inspection done. Now you can use light air pressure (as Fairdeal showed bubbles in his pic) to find the leak..


As for seal direction, the shop manual will show the direction of each.

[boscoe99]

I don’t know where the seals go in both directions in regards to these lower units. Lots of people seem to think vacuum testing should be done. No one seems to know the specs for such a test. So if a lower holds 10psi for 10 minutes but quickly fails a vacuum test, what should be done? Scrap it?

Seals are oriented to keep water out moreso than to keep oil in. See parts book illustration below.

Yes, lots of folks think vacuum testing should be done. Yamaha is just not one of those that think so. Many know better than Yamaha.

Specs for the test are in the applicable service manual. See illustration below from a 30D SM.

If the pressure test fails then the seals or their mating surfaces should be inspected and/or replaced. Or some may say fuuckit, close enough for government work, I am going with what I got.

Isn't the innerweb wonderful? You make me chuckle over on THT. C4 indeed.

[boscoe99]

I don’t know where the seals go in both directions in regards to these lower units. Lots of people seem to think vacuum testing should be done. No one seems to know the specs for such a test. So if a lower holds 10psi for 10 minutes but quickly fails a vacuum test, what should be done? Scrap it?

http://evolution.skf.com/us/seal-analysis-pays/

https://www.google.com/search?biw=12....0.3r6AgAvZVkw