Quote:
Originally Posted by BobMillington
Curious if others have had an issue with shaft seals and sharing my experience.
Recently had my local Yanmar technician replace my oil and water seals on the sail drive shaft. Just hit 760 hours on my Yanmar 4JH4-te w/sd60. My boat is 4 years old and figured I should have those changed out while the boat is on the hard for other service. The Yanmar technician mentioned I had some wear on the shaft, after looking at it with him it was very minor but I could see a faint line were the seal was, running your finger across it you could feel a very slight ridge. This was around the water seal. The sail drive oil was very clean and the water indicator has never triggered in the past. The tech thought the oil didn’t have any water, but recommended I replace the shaft. So I am forking out 750usd for a new shaft. I asked him his opinion as to how frequent the shaft needs replacing and he said since the sd60 has no spacers it may be every time I replace the seals.
Does anyone know how frequent the water and oil sail drive shaft seals need to be replaced? Is there any spacing or other fixes for a shaft with very minimal wear from the seals without a new shaft? I’m thinking I should replace the seals every two years but not sure. Trying to decipher fact from fiction and maybe learn something along the way.
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I am not aware exactly of the manufacturer recommended replacement interval but I have some thoughts. I maintain my own
SD40.
1. Limiting factor on lifespan is the
steel circular spring on the outer seal which is in contact with the (salt) water. When I recently replaced the seals that spring was almost gone, I was just in time replacing the seal. There are non-metallic substitutes available though. Your 2 year interval is more or less what I stick to, though I inspect first and might not necessarily replace.
2. The inner seal 'faces inwards' (function to keep the oil in, spring in contact with oil) and has a much easier life as a result.
3. When putting on the prop (in my case a flexofold with spacer), applying a good amount of grease before sliding on spacer tends to protect the outer spring in my view since the grease is still there at next
inspection (although my seasons are short and my boat is stored on the hard in winter).
4. I have some wear on the shaft but I find the two grooves rather superficial although you can feel them with the nails but I continue with what I have.
5. There is a known issue though with the
SD40 which may not apply to the SD60 which is premature wear on the input shaft. Coupled with excess pressure in the drive due to warming oil + no vent, this led to oil loss on my unit, as evidenced by oil dripping out from under the bell housing.
6. Finally, some users advocate creating an overpressure in the unit relative to the water outside through a header tank and having both seals face inwards. I haven't done this because I am still fixing item 5 above which is caused exactly by having too much pressure in the unit.
On a side note, be aware that the water
alarm on the unit is not related to water in the oil, rather to water entry between the upper and lower seals, so the
alarm alerts you to a potential failure of the lower rubber seal. This is another discussion completely driving a lot of people's decision to stay away from saildrives. Having said that, I recently replaced my lower seal after 18 years of service and it came out looking no different to the replacement I purchased.