Sail drive 120S-E. Wear / groove on the prop shaft at the oil seals

[Viviane2000]

Out of precaution I wanted to replace the oil seals that are on the prop shaft. One to keep salt water out of the sail drive, one to keep the oil inside of the sail drive. When the prop shaft was out I noticed wear, a groove on the prop shaft. After some reading this seems a common problem. See pics. To my surprise there is more wear on the oil side of the seal than on the seawater side..?

• It feels that just replacing the oil seals wouldn't be the smart thing to do. But I'm not sure if this is a lot of wear or quite common. Maybe it looks worse than it is?
• Someone posted that you can replace the 2 seals (9mm thick) with 3 seals, each 6mm thick. The wear will be on a different place on the shaft so that should fix the problem for the next 20 years or so. Is there any reasoning against this?
• Should you place the seals facing: water - water - oil. Or water - oil - oil?
• For the prop shaft of the 120S-E sail drive, are these dimensions correct: outside diameter: 50,80 MM x inside diameter: 31,75 MM. The thickness of the new seals would be 6,35 MM instead of 9,52 MM.
• There are some different materials used to create seals. Is NBR the way to go?
• Does the spring of the seal need to be stainless? Inox?

[geoff]

I think that I came up with the 3 seal idea. So far [about 12 years] it seems to work . I arrange with two keeping water out and 1 keeping oil in . I go for Viton seals as they only seem to use stainless springs . Viton is generally brown . Geoff

[Yngmar]

We sleeved ours. If you search for speedi-sleeve here, you can find lots of information about it. Works fine.

If the inner seal has caused significant wear on the shaft, the oil was not changed soon enough and fine metal shavings from normal wear have accumulated in the oil, making it abrasive.

[Viviane2000]

@geoff thanks for coming up with this solution! I ordered new seals. When these are worn in the shaft it's time to go with the speedi sleeve solution I reckon. But hopefully that's not needed for the next 10 years, and after that I'm not sure if that's still my problem 

@Yngmar your explanation makes sense, when the oil is not changed enough times the metal shaving accumulate making it abrasive. I will be filling my 120S-E with new 75W90 oil, I have read different things online about gear oil vs normal engine oil needed for the sail drive. You have a 120S-E as well right? It needs the expensive gear oil, right?

I want to make sure the SD is clean on the inside from the old oil + dust and grime that worked its way in the SD when we replaced the rubber seal. Any tips on flushing the SD before filling it with gear oil?

[Yngmar]

Volvo Penta changed the official recommendation to engine oil for all models except the 120S-E, which still requires 75W-90 API GL5 gear oil. It's not that expensive, about €8 a liter: https://www.ebay.it/itm/MANNOL-75W-90-SYNTHETIC-API-GL4-GL5-1-LITRO/302913396443

Compared to the cost of a new shaft, 2.6 liter of that is nothing

Usually when you drain it, the dirt comes out with the oil. Flushing it with a load of diesel is possible, but you'll then have to clear that out thoroughly - probably not enough benefit versus the risk of thinning the gear oil unless you want to waste a whole load of gear oil to flush out the diesel with

The drain plug has a recess for a small magnet that collects the metal particles, much like gear boxes in cars have (bigger ones). But for some reason the magnet is absent on most of the saildrives I've seen.

[Keweetoo]

@Vivianne2000  were the dimensions mentioned in your post #1 correct for the 3 seal option? I have a 120S-E saildrive and boat is coming out in a few weeks and the saildrive seals are one of the maintenance jobs to be done. I know last time I looked (4 yrs ago) there was some grooving beginning so I suspect I may need to go down this route. Did you purchase in UK? Thanks

[Viviane2000]

Again, many thanks @yngmar. Maybe I'll flush the SD with a little left over (unused) engine oil I have laying around. Just to easy my mind. A proper flush is probably overkill and not needed.

@Keweetoo, I have some difficulties with online ordering / receiving the oil seals in Italy.. So I haven't received the seals yet. I have to order them again. Until then I cant be sure if the dimensions are correct. But I'm pretty confident they are.

I ordered the seals on this website:
https://www.123bearing.eu/seals/seal/rotary-shaft-seal?fld_diametreinterieur=31.75&fld_diametreexterieur=50.8&fld_hauteur=6.35
The NBR seals should be fine if they have stainless steel springs, Im not sure if these have them. Otherwise order the FPM seals, they should have stainless steel springs.

[Viviane2000]

@Keweetoo the oil seals arrived yesterday, after installing them we MacGyver'ed a pressure test. A 12V compressor + drilled a hole through an old oil plug and hot glued an attachment point for the compressor to the oil plug. The pressure kept stable for more than a minute so we passed the Volvo Pressure test 

So these dimensions are correct: outside diameter: 50,80 MM x inside diameter: 31,75 MM. The thickness of the seals can be 6,35 MM or 9,52 MM.

"Connect the pressure gauge to the oil drain hole. Pump the pressure up to a level not exceeding 78 kPa (11.31 psi). Check that the pressure remains constant for 1 minute."

[Keweetoo]

Viviane2000 - many thanks for that confirmation.

[elias]

What a great tool you made , congrats !

[JEN-et-ROSS]

@Keweetoo the oil seals arrived yesterday, after installing them we MacGyver'ed a pressure test. A 12V compressor + drilled a hole through an old oil plug and hot glued an attachment point for the compressor to the oil plug. The pressure kept stable for more than a minute so we passed the Volvo Pressure test 

"Connect the pressure gauge to the oil drain hole. Pump the pressure up to a level not exceeding 78 kPa (11.31 psi). Check that the pressure remains constant for 1 minute."

Interesting idea, but did the test pressure not vent via the dipstick (or filler cap)...?   Bill..

[Viviane2000]

Interesting idea, but did the test pressure not vent via the dipstick (or filler cap)...?   Bill..

The oil filler cap and dip stick both have a rubber ring. Apparently completely sealing them.

The pressure test is mentioned in the Volvo Penta Workshop manual, it's not something we invented our self The adaptor to fit an compressor to the oil drain plug is a DIY-fix.

[marioxp]

One question for everyone, when you change the inner and outer semering of saildrive shaft, do you grease it with some grease, maybe with marine grease?

The screws that hold the saildrive housing, and the screws that hold the zinc anode, do you grease it? These screws are stainless steel and go into aluminum, maybe it would be good to grease them with anti-corrosion grease (Duralac) or grease to lock screws?

[geoff]

Grease on the seals/shaft,and loctite on the anode allen screws. Geoff