Yanmar Saildrive SD20 oil between diaphragms

magdalena

magdalena

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My Yanmar SD20 Saildrive has two rubber diaphragms to keep the water out of the hull, with a water detector between them. The detector sounded an alarm while we were motoring this afternoon. Removing the detector and pumping out liquid from between the diaphragms brought out a small amount of water and a large amount of gear oil.

Should there be gear oil between the two diaphragms? Any thoughts on where it might have come from?

Thanks in anticipation.
 
magdalena said:
My Yanmar SD20 Saildrive has two rubber diaphragms to keep the water out of the hull, with a water detector between them. The detector sounded an alarm while we were motoring this afternoon. Removing the detector and pumping out liquid from between the diaphragms brought out a small amount of water and a large amount of gear oil.

Should there be gear oil between the two diaphragms? Any thoughts on where it might have come from?

Thanks in anticipation.
Click to expand...

I've occasionally removed the seal detector/sensor from my SD20 saildrives and there was nothing in there, oil or water.

Richard
 
magdalena said:
My Yanmar SD20 Saildrive has two rubber diaphragms to keep the water out of the hull, with a water detector between them. The detector sounded an alarm while we were motoring this afternoon. Removing the detector and pumping out liquid from between the diaphragms brought out a small amount of water and a large amount of gear oil.

Should there be gear oil between the two diaphragms? Any thoughts on where it might have come from?

Thanks in anticipation.
Click to expand...
Can't comment from direct knowledge of the SD20, but I'm sure that gear oil shouldn't be present between the diaphragms, and that could point to a fairly serious problem.
AFAIK, the diaphragms are at or very near to the position where the upper and lower gear-cases join, so a joint failure here might be a reason.
Can't really suggest where the water came from, except perhaps via the diaphragm itself, or is there a cooling water channel through the gear-case joint that is leaking?
In any event, loss of lubricant can be very damaging to a saildrive, as a pal of mine found out. I suggest that you at least check the oil level and arrange close inspection of the diaphragm and drive leg ASAP.
 
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Thank you for your thoughts. I have used the hole where the water detector screws in to pump out the oil and water from between the two diaphragms. I am working on the assumption that it got in from above (the second seal presumably works by water pressure underneath, so any oil or water than falls on top appears to be able to quickly make its way in the void between the diaphragms - certainly I was able to push it down with my finger on the inside (saildrive rather than hull) edge). I will inspect it again in when I am next on board - hopefully it will be dry and oil free, confirming my theory...
 
With oil and water in the space, I would guess that the top skirt type diaphragm seal is no sealing properly. However the oil and water could also be coming from the joint between the lower gear housing ... the leg, and the upper part .... connected to the engine. If so you will probably have water in the gear oil in the leg so check the colour of the oil.

I have never taken mine apart, so I have no practical experience on this.
 
I took my SD20 out and changed the diapragms last winter. There should be no oil or water between them. The oil must have come out of the sail drive unit. There is an o ring seal between the head sectrion and leg section and I expect this is the problem.
I wrote a 3 page summary of my experiences changing the seals which I will PM you if you wish ( get in touch this morning as I am sailing from this aft and all next week with no internet.)
Changing the seals is a job within the scope of most practical boat owners but you will need to be out of the water and it takes time and the parts are expensive
all the best
Martin
 
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