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Old 16-03-2016, 00:15   #1
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SD50 Oil Leak

My Yanmar SD50 is leaking gear oil where the saildrive meets the hull. It is weeping from between the large circular flange that is bolted to the hull.
I assume it is leaking from the leg and making its way out at this point. Its definitely gear oil (not engine oil) and does not seem to be coming from the dipstick hole on the top of the drive above. Any suggestions as to where the oil may be coming from.

Where are the oil seals in an SD50 - i had thought that they were only where the drive joins the engine and the lower seals behind the prop shaft? However failure of neither could explain my leak.

I'm not sure if this is connected but I have noticed oil level fluctuations in my drive (up as well as down) and i suspected water ingress through the lower seals. However I just changed the oil and there does not seem to be any evidence of a water leak - or at least a major one with visible signs of water in the oil.

Thanks in advance

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Old 16-03-2016, 00:35   #2
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Re: SD50 Oil Leak

i just went thru haulout exercise, worried about water same as you, and mechanic checked oil. No sign of water so no seals change needed.

I also get varying level on dipstick. If you get that and you worried, undo nut on the top of saildrive where is says oil and air pressure will equalize immediately and you should get correct reading.

Oil ... maybe you spilled it and now can't clean it properly ?

there is lots of negativity about SD 50 on internet, probably couple of disgrunted customers raising noise, so you need to do your own checking.

My saildrives are after cone service in great condition after 500 hrs.

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Old 05-08-2016, 08:22   #3
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Location: Germany
Boat: Fountain Pajot, Belize 43, 43ft
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Re: SD50 Oil Leak

Hello Carmelo,
when you have water in your saildrive, the oil didn't look golden, it has a color like grey cream .
Yanmar has changed oil dipstip. (I didn't find the page at the moment) But when you reduce the oil level close below to the min it should work.
The root cause is the following: when the saildrive is heated up, the remaining air space is to less. The internal pressure is to high and the oil spills out at the shaft seal to the engine.
See the document here: The Infamous Yanmar SD50 Dipstick... - myHanse - Hanse Yachts Owners Forum

Best regards
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Old 06-08-2016, 01:06   #4
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Boat: Fountain Pajot, Belize 43, 43ft
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Re: SD50 Oil Leak

Hello Carmelo,
I found the document:
seach for:
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Old 06-08-2016, 04:58   #5
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Re: SD50 Oil Leak

The SD-50 has an upper gear housing and a lower gear housing. The lower gear housing is the drive leg on the outside of the boat and the upper is the gear box inside the boat. They are connected together by a piece called the middle plate. There is an o-ring seal on the top and bottom of the middle plate. The outer water seal fits over the middle plate, so if oil is coming out between the water seals it is likely that the upper o-ring seal between the middle plate and the upper housing has failed. If it's running down the outside of the drive leg then the lower o-ring has probably failed.
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