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Bonaire 26-05-2009 05:27

Yanmar SD 20 Saildrive Seals
We have been getting water mixed with the oil in the saildrives almost inmediately after the seals were replaced, the last two times.

We have learned in this forum that we missed replacing the two o rings, in addition to the seals.

We have also learned that "hammering" in the seals, as the expert mechanic did, is NOT the right way of installing them.

We also suspect that the spacer between te seals was not installed, we will soon know.

We now plan to do the job ourselves and our question to the forum is:

Can someone please show us on the diagram or let us know the part number on the diagram, for the "frozen nut" that is mentioned in some postings sometime ago.

Another question would be:

Can we fit two water side seals and one oil seal in the same cavity?
Maybe not but maybe someone has thought about this before.



imagine2frolic 26-05-2009 05:43

There was a long thread here about that, and the blown apart picture was with it.....i2f

Tellie 26-05-2009 06:34

Attached Thumbnails

Bonaire 26-05-2009 09:44

Thank you i2f, we had saved the pictures in our files.

On the thread that you refer to the "frozen nuts" are mentioned but we can not identify them from the pictures.

If anyone can help me identify them it will be appreciated.


imagine2frolic 26-05-2009 12:37


Pretty boat!!!!!!!!!!

Can you describe where they are? Behind, or before a certain part? Tellie brought the pic up, and I don't know how to enlarge it, but I can look in my manual on the boat with some description of which part to look for......i2f

Bonaire 26-05-2009 14:00

Thank you i2f for the compliment, she is not only nice looking but sails fast too !!

That is preciscely the problem with these "frozen nuts", that we do not know where they are !!

Can not find that thread where they are mentioned, can you guide me to it?
We are still a bit green at this site !

Regards and thanks for the help.


TaoJones 26-05-2009 14:10

Is this the thread you're looking for, Bonaire?

If you scroll down to ssullivan's post #36, he mentions "frozen" nuts there.


imagine2frolic 27-05-2009 08:55

Good search Tao......that's the one I was looking for......i2f


Do you have any interior shots of the boat?

Bonaire 27-05-2009 14:47

Thank you Tao and i2f, that is the one !!
I2f I will post a few internal pictures of our boat in the next few days. (one we work out how to do it!)

Thanks again,


imagine2frolic 27-05-2009 15:13

I know the feeling.........i2f

Bonaire 27-05-2009 15:32

Thank you all, we now know that the "frozen nut" is nut #45 and it would seem (??) that it does not need to go out to change the seals, only if you want to inspect or replace individual components on that horizontal shaft.

We happen to have two new rear assemblies (where the seals and rings go) so we plan to install the seals and rings in a "controlled" environment and be ready for when we haul out.

When we do this we plan to check and see if two water seals can be installed....will keep those interested posted.
In the mean time, we will continue replacing whatever oil we can and as frequent as about 50 hours or so.



Jacana 11-01-2010 14:35

SD20 saildrive
Anyone have a diagram of clutch assembly of sd20 .When engaged no prop motion fwd or reverse.Coupled to 3gm30 yanmar currently 2300hrs and engine used daily.If you have had the same problem I would appreciate any advice.Thanks Geoff.

JustCatamarans 11-01-2010 15:46

There is no clutch cone in the 20,s just a dog gear that moves uo or down, engaging with the fwd or reverse - great system.
The lower shaft seals - the one closest to the prop must have the spring facing the sea, the inner seal must have the spering facing the oil side. If these seals are not installed in these directions you will get failure. The saildrive is non-vented, so any internal pressure is kept in check by the inner seal, and water pressure is kept in check by the outer seal.
Between the two seals must be two shims(not critical). i fill the seals and the gaps between them with lithium grease, especially the one facing the salt water. Check the prop shaft for grooves where the seal lips run, you can have this repaired, or move the seals slightly.
Do not use regular 90w gear oil, use Mercruiser outdrive oil, the co-efficient of expansion is lower on the Mercruiser, thereby reducing the internal operating pressures, thereby saving the seals. On new saildrives, if you do not use this oil you will void your warranty.
I suggest chaning the lower seals every 2nd time you paint the bottom, ie every 2 years.
The O-rings must be replaced.

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