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Old 02-10-2019, 16:34   #1
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Yanmar SD20 Oil seals query

Hi everyone,
I have just done an oil seal change on my SD20's. I was unable to get the genuine Yanmar seals because of where I am. Instead I used the exact same size seal made by SKF. (HMSA10 RG to be exact)

My question is this.... Does anyone know if the genuine Yanmar oil seals have a stainless spring inside the seals?
If yes, what should I now do, is it likely that the SKF seals will fail within 1 years use as a result.

I really didn't think about this until after the job and I now feel like a true plonker.

thanks everyone in advance
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Old 02-10-2019, 16:46   #2
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Re: Yanmar SD20 Oil seals query

Sorry don't know if Yanmar have ss spring but if spring is on the oil side not seawater side it should be fine.
What is often done is use an o-ring instead of the spring if facing water side. I do this on raw water pumps as don't like paying yanmar $50 for a $3 seal
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Old 02-10-2019, 17:45   #3
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Re: Yanmar SD20 Oil seals query

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Originally Posted by Compass790 View Post
Sorry don't know if Yanmar have ss spring but if spring is on the oil side not seawater side it should be fine.
What is often done is use an o-ring instead of the spring if facing water side. I do this on raw water pumps as don't like paying yanmar $50 for a $3 seal
interesting thanks.
The seals in the SD20 sit back to back, they are the same seal in part number. I realise the oil side wont matter because it is constantly submerged in oil. My worry is that the spring on the sea water side will corrode in 3 days and break.

on the plus side, I did bury it in waterproof grease whilst building it, I hope that provides a good amount of protection.
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Old 03-10-2019, 06:31   #4
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Re: Yanmar SD20 Oil seals query

Yep, the Yanmar seals have stainless steel springs and if your'e in a place where it's hard to get the genuine ones it's possible to very gently remove the garter springs from the old original seals and put them in the new commercial SKF seals. Only use the inner seal garters because they'll be in pristine condition and if they get even a little bit stretched then either go back to the plain steel springs or do the oring thing
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Old 03-10-2019, 07:38   #5
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Re: Yanmar SD20 Oil seals query

Thanks for the clarification, unfortunately the old seals went in the bin before I realised this problem. I think I'm going to stick with the SKF seals as they are and make sure to change the seals again in 12 months.
Perhaps I should keep an eye on the oil level, if it increases I would assume sea water has entered the housing.
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Old 03-10-2019, 10:04   #6
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Re: Yanmar SD20 Oil seals query

If you get water the oil will show bubbles after running. Also if you ever get in a bind I have parts for the sd-20's that I took off my cat that was destroyed in hurricane Michael. pay shipping and they are free . the housing had electrolysis
thats why I had to replace them.
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Old 03-10-2019, 10:49   #7
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Re: Yanmar SD20 Oil seals query

If your seal become compromised and water enters then the oil will turn milky. The bubbles mean nothing.
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Old 03-10-2019, 13:20   #8
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Re: Yanmar SD20 Oil seals query

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Originally Posted by rancher44 View Post
If you get water the oil will show bubbles after running. Also if you ever get in a bind I have parts for the sd-20's that I took off my cat that was destroyed in hurricane Michael. pay shipping and they are free . the housing had electrolysis
thats why I had to replace them.

That is very kind of you indeed, thank you.
I have not yet had the boat in the water, bought her 6 months ago and been working on her full time ever since. She is getting close to a trial run now so I don't know for sure if the SD20's are good and behave normally whilst under load.
So if I find huge problems I would be very grateful to take you up on that offer, I would never accept them for free, but we can do a good deal


It doesn't look like anyone is 100% sure if the genuine Yanmar oil seals have stainless springs in them or not. The guy at the machine shop didn't think they existed actually. So maybe the job was done as well as it could be done... who knows.
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Old 03-10-2019, 14:42   #9
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Re: Yanmar SD20 Oil seals query

Skipperpete in post #4 said they had stainless springs & I suspect he knows
I've never worked on a SD50 but I did work on a ladyfriends raw water pump that had 2 oil seals to keep the water out.
Can't remember how they were installed originally but I put standard oil seals in spring sides facing each other & filled them with waterproof grease. That was over 10 years ago & they are still working. This was before I knew the o-ring trick.
However it doesn't get used much & its in fresh water now.
I wouldn't have any clue as to how long the grease will stay there if its facing the seawater but you can always dive down & have a look.
Suspect, but don't know, that synthetic grease would last a fair while.
As other posters said, check if oil turns milky.
Have seen another thread where they riggged up their sailldrive with an oil header bottle so it had positive pressure in the leg. Sounded like a good plan
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Old 03-10-2019, 15:49   #10
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Re: Yanmar SD20 Oil seals query

[QUOTE=
Have seen another thread where they riggged up their sailldrive with an oil header bottle so it had positive pressure in the leg. Sounded like a good plan[/QUOTE]

I have done this to tide me over until next slipping. I found oil does seep out the bell housing probably from the SD20 spigot seal. Good idea but untidy for the longer term.
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Old 06-10-2019, 05:48   #11
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Re: Yanmar SD20 Oil seals query

Quote:
Originally Posted by Compass790 View Post
Skipperpete in post #4 said they had stainless springs & I suspect he knows
I've never worked on a SD50 but I did work on a ladyfriends raw water pump that had 2 oil seals to keep the water out.
Can't remember how they were installed originally but I put standard oil seals in spring sides facing each other & filled them with waterproof grease. That was over 10 years ago & they are still working. This was before I knew the o-ring trick.
However it doesn't get used much & its in fresh water now.
I wouldn't have any clue as to how long the grease will stay there if its facing the seawater but you can always dive down & have a look.
Suspect, but don't know, that synthetic grease would last a fair while.
As other posters said, check if oil turns milky.
Have seen another thread where they riggged up their sailldrive with an oil header bottle so it had positive pressure in the leg. Sounded like a good plan
unfortunately diving wont help unless I was to remove the prop and anode. You cant see the seal when the lower unit has those attached you see.

I also suspect the Grease will do a fairly decent job, if only for one year I will be happy.
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Old 06-10-2019, 13:13   #12
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Re: Yanmar SD20 Oil seals query

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Originally Posted by broken pete View Post
unfortunately diving wont help unless I was to remove the prop and anode. You cant see the seal when the lower unit has those attached you see.

I also suspect the Grease will do a fairly decent job, if only for one year I will be happy.
Yes I realised after I posted diving was probably a dumb suggestion
Should think more before posting!
I suspect you are right about the grease too but, if you remember, please let us know what happened in a years time.
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Old 10-10-2019, 11:50   #13
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Re: Yanmar SD20 Oil seals query

I sure will, there is a good chance the genuine yanmar seals are not stainless either. I love the idea of using an O ring, that will be next years solution
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Old 10-10-2019, 12:15   #14
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Re: Yanmar SD20 Oil seals query

Not to hijack the discussion, but I have wondered why the seals on the lower unit were positioned as they are. The water seal is on the outside and the oil seal is on the inside, with the spring side facing the water for the water seal and of course the spring sitting in oil for the oil seal. It seems to me that if the water seal was on the inside and the oil seal on the outside, water would still be prevented from entering the case. Initially at least the the seal springs would still be bathed in oil and later perhaps an oil water emulsion, probably still superior to pure sea water. In the SD60 at least this could be done to shift the wear points on the prop shaft since it's made of unobtainium.



A personal observation on Yanmar brand seals. I have seen no evidence that Yanmar oil/water seals have stainless springs. Every water seal I have changed, and that's quite a few in the 14 years I have owned the boat, has had a severely rusted spring even though they were well packed with grease when they were installed. If they're stainless, it's not very good stainless. Of course there's never any rust on the oil seal spring.
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Old 10-10-2019, 13:58   #15
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Re: Yanmar SD20 Oil seals query

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Originally Posted by Captain Bill View Post
Not to hijack the discussion, but I have wondered why the seals on the lower unit were positioned as they are. The water seal is on the outside and the oil seal is on the inside, with the spring side facing the water for the water seal and of course the spring sitting in oil for the oil seal. It seems to me that if the water seal was on the inside and the oil seal on the outside, water would still be prevented from entering the case. Initially at least the the seal springs would still be bathed in oil and later perhaps an oil water emulsion, probably still superior to pure sea water. In the SD60 at least this could be done to shift the wear points on the prop shaft since it's made of unobtainium.



A personal observation on Yanmar brand seals. I have seen no evidence that Yanmar oil/water seals have stainless springs. Every water seal I have changed, and that's quite a few in the 14 years I have owned the boat, has had a severely rusted spring even though they were well packed with grease when they were installed. If they're stainless, it's not very good stainless. Of course there's never any rust on the oil seal spring.
Re seals orientation: That was my theory as well when I rebuilt a raw water pump which had 2 seals in it, see post#9. It has the added benefit of trapping the waterproof grease between the seals instead of exposing it to the sea water turbulence from the spinning shaft.
Interesting that the mafias seal springs aren't stainless. Not that I'd ever buy a seal from them anyway when you can getthe same thing from bearing/ seal places for 1/10th of the price, down here anyway.
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