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Old 31-07-2016, 03:51   #1
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SD20 oil leak, but from where?

Here's hoping for advice from this knowledgeable forum.

I have just hauled the boat because of water in the SD20 saildrive oil, the obvious assumption being the prop shaft seals have failed (10 years old).

I had thought that on hauling the boat, the oil would leak out from the prop end. However it actually leaks out of the leg from the front end where there is a large square hole as in the enclosed pic.

The exploded diagram doesn't help much, so where could this be coming from and how do I fix it?

Any advice much appreciated.
Grant
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Old 31-07-2016, 05:43   #2
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Re: SD20 oil leak, but from where?

Yanmar Saildrive Seal Leaking . . . Again
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Old 31-07-2016, 06:16   #3
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Re: SD20 oil leak, but from where?

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Originally Posted by GordMay View Post
Thanks.
I had seen this thread but I am not sure it addresses the problem I'm getting. I can't see how the water gets into the leg (and then of course out again) when there is apparently no connection between the two. What am I missing?
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Old 31-07-2016, 11:00   #4
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Re: SD20 oil leak, but from where?

Googled it and found several links and a few similar cases and a case of oil between diaphragms no one had a definitive answer . Are you positive it is fear oil? Smelled it etc? Has a distinct nasty somewhat fishy smell. Have you pulled the sensor and checked between the diaphragms?

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Old 01-08-2016, 18:38   #5
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Re: SD20 oil leak, but from where?

I think that large square hole you mention is also part of the engine cooling raw water intake.
That's what I was told by a Yanmar mechanic when I asked him about its purpose when my boat was on the hard last year.
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Old 01-08-2016, 19:20   #6
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Re: SD20 oil leak, but from where?

First, sail drives have two seals on the prop shaft. One keeps the oil in and the other keeps the water out. They are the same seals but face opposite directions. It is perfectly possible and some might say normal to have one fail and not the other. Just because water leaks in does not mean oil will leak out. These seals only seal in one direction. Second, sail drives have a top half and a bottom half with an o-ring seal in between, It is possible for this o-ring to fail and allow oil to get to the water intake hole and water to get into the oil. When the drive gets hot pressure in the case will force the oil out and when it cools it will suck the water in. Welcome to sail drive ownership.
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Old 02-08-2016, 06:11   #7
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Re: SD20 oil leak, but from where?

Thanks to you all and particularly to Captain Bill for his welcoming me to saildrive ownership. It is a club the membership of which I am finding it increasingly hard to appreciate.

The probable final answer here after searching the memories of local engineers and the internet (but unsurprisingly no response from the Yanmar UK importers), is that Captain Bill's suggestion is probably the best answer. I'll change the oil and continue to use it until haul-out which this year is only a few weeks away, and then change the O ring.

Huge thanks to you all

Out 42
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Old 02-08-2016, 11:12   #8
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Re: SD20 oil leak, but from where?

Some have run with leaking seals / water in the oil for extended (years) periods (years) with no apparent negative impact. Know of one guy who did for 5 years then pulled the saildrives apart in his shop and there was zero deterioration. Everything spec'd out perfect. Not recommending it, but maybe looks worse than it is.

Bill
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Old 02-08-2016, 12:47   #9
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Re: SD20 oil leak, but from where?

Thanks Moontide

It doesn't surprise me but I'm not sure why. My understanding of water, oil and metal is based in hot automotive applications. I suppose the absence of heat in a drive leg allows the lube stick to the metal rather than letting the water get to it but that is quite probably fantasy.
I'm going to run the rest of the season out and then probably strip the leg to see what's gone on. I'll then post back here.

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Old 09-09-2016, 09:27   #10
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Re: SD20 oil leak, but from where?

[quote]
.... I suppose the absence of heat in a drive leg allows the lube stick to the metal rather than letting the water get to it but that is quite probably fantasy....
[unquote]

One of the latest Yanmar SD20 tech sheet recommends to use the dipstick LOWER mark as the HIGH one, giving it more air volume to expand. And use Quicksilver 90 gear oil, as it "allegedly" keeps the oil/water mix "separate".
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Old 09-09-2016, 12:37   #11
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Re: SD20 oil leak, but from where?

Thanks to all of you for responding. It's getting close to leg strip time, and I reckon I will probably go with a breather setup as others have done when I put it all back together.

Happy sailing
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Old 11-09-2016, 06:11   #12
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Re: SD20 oil leak, but from where?

I mounted a header/expansion tank 1 1/2 feet above the waterline more than 12 years ago, and have never looked back. Also, makes checking and adding oil much easier.

I use Amsoil which supposedly can tolerate 10% water (or something like that.

The other thing you might check is the o-ring on the drain plug.You have to be very careful that it seats correctly. I don't think the Yanmar o-ring, or any other that I have found, fits the plug screw properly.
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Old 11-09-2016, 07:37   #13
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Re: SD20 oil leak, but from where?

Thanks Ggray. The header tank sounds the way to go, so that's the plan.
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Old 11-09-2016, 08:25   #14
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Re: SD20 oil leak, but from where?

I think somewhere in these sail drive discussions I described the system and parts that I used.
Good luck, but don't forget about that drain plug o-ring!
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