Yanmar SD20 Saildrive Oil Seals - Water in Drive

[Cotemar]

Sonosailor,

Just go to any junkyard and get a VW antifreeze overflow tank as show in the above post.
Their cheap and every junkyard has a few.

[ggray]

Cotemar, that looks real good,but it also looks to be much larger in diameter than what I made. And it would be be good to make sure the tank is vented as well. I've seen radiator tanks that were designed to be pressurised.

Sonosailer, I didn't change my fill cap; I just drilled out the hole the dip stick was screwed into. Then with my vise I pressed a short piece of 1/4 inch ss tube through the hole until it extended down to the proper oil level. If you can flare the top end of the tube a tiny amount it may help keep the tubing tight on the tube.

Next time on the boat I'll try to remember to snap a picture.

[Cotemar]

ggray,

The picture came from a user doing exactly what you are doing.

VW antifreeze overflow tanks are vented. I have 2 VW Jetta's in my driveway that have these same overflow tanks.

http://www.cruisersforum.com/forums/...tml#post637464

[ggray]

My mistake; the cap looked so robust it looked like it was made for pressure.

[Sonosailor]

I'm back in Canada, having replaced my bearings, and still considering this modification for when I return. The VW tanks look like a great idea. Any other tanks work well? I guess you'd want to have a valve on that piping close to the saildrive cap. Do you remove the piping to check the saildrive, or do you just keep your eye on the tank and not bother?

[perchance]

The first thing you need to do is a pressure test on your drive and try to see where the air bubbles are coming from. You will have to dive the boat if in the water to do this.
Seal failure can be caused by fishing line, shaft grooving or just plain old age.
Leaving water contaminated oil in the drive will cause your bearings to rust and fail in short order.
If you have to haul out to change seals look closely at you magnetic drain plug if it has one and examine the wear metal on the magnet.
Small furry looking filings are normal wear, but flakes or chunks are a sure sign of imminent failure.
Depressurising a sail drive that was designed to be pressurised may not be an ideal solution but adding a monitor bottle makes perfect sense as you can tell at a glance if your drive oil is going down.
Positive pressure does keep the water out if the seals are not compromised. The problem occurs when the drive cools off and a vacuum is created drawing water in past the seals.

[Rapanui]

The charter company that operate our boat in Croatia have to deal with this problem a lot with both Volvo and Yanmar saildrives. Most mooring is stern to using mediterranean mooring and requires picking up lazylines from the stern and using these to secure the bow. Inevitably people get them round the saildrives from time to time and this causes the saildrives to leak. A lot of people also tow fishing lines which they forget about when manoeuvring and there is nothing better for cutting a seal up. The company automatically replace the saildrive shaft seals each year in the winter haul out and most boats, even brand new, show signs of milky oil by August.

They deal with this by using an oil extractor and regularly pumping out the milky oil and replacing with fresh. They don't get any long term problems with the saildrives provided they keep on top of it. This could keep you going until you get to a planned haulout when you can service the seals. Our first Yanmar engines and saildrives had done over 5500 hours each and were still perfectly serviceable but had lived with the issue and this maintenance regime for most of its life. Its a pain but not a tragedy.

[ggray]

Originally Posted by perchance

The problem occurs when the drive cools off and a vacuum is created drawing water in past the seals.

I'm not certain it is that simple or predictable. You would need to consider the coefficient of thermal expansion of the oil, the aluminum housing, the steel parts (gears, etc). I have no clue what it is for the oil, but aluminum is about double that of steel, IIRC. It could be that a partial vacuum is created as the saildrive heats up, contrary to what I first assumed, and a pressure increase with a drop of temperature. (I first came up with this reasoning when I discovered a pool of oil around the top of the saildrive after the first deep freeze.)

Whatever it is, I believe we have a constantly changing pressure differential inside the sealed SD relative to the atmosphere. An expansion tank, to me, was an obvious solution.

[Sonosailor]

Back to the reservoir: I paid $25 for one out of a VW Jetta, and have brought it home and attempted to clean it up. I don't like it:

1. It is way larger than is required. I suggest anything that holds 1/2 cup or more would be more appropriate.
2. It has a separate inlet and outlet, and a vent, meaning some modification is necessary. Also the outlet on the bottom is larger than necessary, somewhere around 5/8 to 3/4 inch. It will take some reducers.
3. The interior is convoluted, so that I can't get it clean. The dirt from the previous use is still in there, ready to be delivered once it finally lets go.

I'm going to keep looking for something smaller. Did you guys put a valve on the line? Do you have to disconnect to remove the saildrive cap?

[Sonosailor]

I found a little plastic rotomolded tank that came off a Pontiac Sunfire, and was meant to deliver fluid to some part of the car's clutch system. It was perfect, with a single small outlet, but the yard would not sell them separately from the part it was lubricating.

If you have a Pontiac Sunfire, keep your hood latched, 'cause I'm on the prowl. ;-)

[careka]

Originally Posted by Sonosailor

I found a little plastic rotomolded tank that came off a Pontiac Sunfire,
If you have a Pontiac Sunfire, keep your hood latched, 'cause I'm on the prowl. ;-)

Just by one, take the tank and dump the rest.

[ggray]

Originally Posted by Sonosailor

I'm going to keep looking for something smaller. Did you guys put a valve on the line? Do you have to disconnect to remove the saildrive cap?

I put a pinch valve on the tube just above the cap. I don't disconnect to remoe the tank, but when I screw the cap on, I first twist the cap and tube counter clockwise so once the cap is screwed in, the tube won't be twisted.

And I just look at level in tank to see if I need to add oil.

If you are still looking for a smaller tank, what I used works fine.

[TabbyCat]

We are on the hard and want to replace our oil seals. Does anyone have a manual? Have got as far as pulling off the propeller, but the cover assembly does not want to budge. Do we need a puller, or will it just spin off? We have gotten it to rotate an inch or so.

[Cotemar]

Here is the Yanmar SD20 Saildrive manual

http://www.marathondiesel.com/site/i...n%20manual.pdf

That cover should come right off with the help of a screw driver to pry on top and bottom so as not to bind it and do it evenly

[TabbyCat]

Thanks, that's what we were hoping. The link to marathon diesel didn't work. Any chance you could e-mail the pdf to me?
Sailor 'at' tabbycat.us
Thanks!