SD20 Prop shaft seal orientation

[Halo]

Hi All
The oil in my Yanmar SD20 sail drive has turned to egg yolk. This means water is getting in. I replaced the drain plug o ring last time out of the water so I am now replacing the prop shaft seals. I suspect the seals may have been put in the wrong way round last time. I have the service manual but cannot make out for sure if the hollow side should be on the sea water and oil side ( both blank faces facing each other) or with the two hollow sides together in the centre. Can anyone say for sure ?
Thanks

 

[RichardS]

The spring must always face the liquid that it is intended to contain.

The outer seal therefore has the spring facing towards the seawater and the inner one has the spring facing towards the saildrive oil.

I filled the space between the two where the spacer rings go with waterproof grease. I also bought extra spacers so I could move the seals slightly down the the shaft onto a better profile. I think that I also used twin lip seals.

Richard

 

[Halo]

Thanks Richard
Do you have a part number for twin lipped seals ?

 

[rogerthebodger]

I agree with Richard that the spring must face the fluid that you are sealing against.

This is a classic example when a double spring seal can be uses which tend to be thinner than 2 seperate seals

Don't get confused between twin lip seals and single lip + wiper seal.

In your case you don't need the wiper as the wipers will face each other and do nothing. It won't harn to fit a seal with a wiper but won't be any advantage.

 

[RichardS]

Thanks Richard
Do you have a part number for twin lipped seals ?

The Yanmar seals part number 196313-02591 are actually NOK AC2081E 35.55.8 seals.

Simply Bearings sell a number of seals of this size and provided that they are stainless steel spring, any of them would work. The twin lipped versions are more expensive so you would need to compare these with the Yanmar originals.

I remember now that I actually used the Yanmar ones as it wasn't until I got the thing apart that I could see that they are standard 35.55.8 seals.

You will also need the two O-rings 24321-000950 and a drain plug seal 24341-000125 although I have never removed the drain as it's just one more thing to go wrong.

The spacers are 196315-02880 but if your shaft is in good condition you won't need these.

Richard