Saildrive - water in oil

[brianc]

Originally Posted by 2Hulls

Huh? Do you not own the boat?

Dave

I co-own the boat...

[brianc]

Thanks for the input!

Originally Posted by belizesailor

Sometimes the seals will leak a little after the initial installation or if prop/shaft get fouled/impacted hard. Try extracting the oil/water via the fill, fill with clean oil and run again. If no water then may have just been a one time event.

Yep, that's happening early next week. I'm not getting my hopes up for a one-time-event but we'll see. At least it'll be clean oil on the way to the yard. If it's only $450 for a Volvo part I'll be pleasantly surprised!

Originally Posted by a64pilot

NEVER re-use the O-ring, they are just too cheap not to replace every time, but most mechanics will re-use the O-ring. ... I assume you have to haul the boat to do anything?

I do remember him re-using the o-ring last time so I'll get that addressed as well. Yes, we'll be hauling out probably next week...third time in the past year; first for the original saildrive water/oil fix and bottom paint, second for repair from a collision (not my fault, someone hit us in the marina), and here we go again!

Originally Posted by SV THIRD DAY

We cruised with a couple in mexico that literally carried a spare saildrive under their bunk for a quick haul and swap.

I only had space for a spare engine, batteries, and water pumps...

So it seems like I'm looking at:
1. Shaft seals need to be replaced [again] because of impact or some type of fouling
2. O-ring failure or failure to replace the o-ring
3. Possible wear or something on the shaft causing the shaft seals to fail quickly
4. Boot sealant failure (from the linked post)

Guess we'll find out soon...

Thanks again - Brian

[2Hulls]

Originally Posted by brianc

I co-own the boat...

Are you at least allowed to watch work being done?

Assuming you are, be there for the disassembly of the lower unit. First they'll drain the oil and remove the prop and zinc then remove the seal assembly (called the bearing housing on the Volvo exploded views).

Check for the drain plug o-ring. This may reveal itself right away after haul if oil drips develop. Likewise look for drips coming around the shaft once the prop and zinc are off - or maybe even before they come off. Look for drips coming from the joint between the seal assembly and sail drive leg. This is the joint just forward of the zinc and may be painted over. There are two large diameter o-rings that make up this seal.

To remove and disassemble the seal assembly they may use a puller or just pry the assembly away from the sail drive leg. Check for both large diameter o-rings when it comes off. Once removed, they have to press out the bearing race to get at the two shaft seals that are installed back-to-back. Very important >> when they remove the old seals, make sure they are facing in opposite directions! The outer seal should face out - to keep water out. The inner seal should face in - to keep oil in. The "face" of the seal is the side with the visible little spring. The other side is flat. the two flat sides of the two seals should be touching together. If the outer seal is facing in, there's your culprit and you should have this work being done for free since they hosed it up the last time.

If the shaft is scored where the seals ride, this doesn't necessarily mean you have to buy a new shaft. There's a nifty cheaper fix available >> Speedisleeves >> SKF Speedi-Sleeve Here's a cool YouTube video >>

http://www.youtube.com/watch?v=09LiVbqL6ss

Good luck,
Dave

[brianc]

Thanks for the info, Dave. I usually try to be there for any work that's done as long as I can get time off from my job! I'll definitely be there for this though and your info will be very helpful.

Brian

[brianc]

Quick update - they pumped out the oil, replaced it, ran it for a bit, pumped it out again and replaced it, then ran it at the dock for a while and everything looks good.

I also went out yesterday and motored for probably an hour and it still looks ok...so I guess we're just in monitoring mode until something else happens.

I'll probably try to go out for a few hours this weekend to see if anything turns up. Fun times.

Also, and I'm assuming this is normal, when I open the dipstick you can definitely hear air being sucked in through the cap so there is definitely lower pressure inside...normal?

[belizesailor]

That's good news. Probably just a one time event.

What you hear, or should hear, is air escaping not being sucked in...these drives develop a slight positive pressure during operation.

[2Hulls]

Originally Posted by belizesailor

What you hear, or should hear, is air escaping not being sucked in...these drives develop a slight positive pressure during operation.

I've also heard air when opening the dipstick - usually long after the last run since I check the oil right before the first daily start - but I don't know whether it's sucking or blowing - and I bet it doesn't have to be the same for each drive in each location. It's reasonable to expect that some heating takes place during operation and any air in the system expands, creating pressure. But whether this pressure dissipates or becomes a vacuum probably depends on the ambient conditions and the time between shutdown and opening the dip stick, e.g., it would be hard to believe that positive pressure would persist for a long time in cold water. The way to find out whether it's sucking or blowing would be to slop up the dip stick with soap bubbles and slowly crack it open. But either way, if there's either positive pressure or vacuum some time after the last run, that means the seals are holding something....

Dave

[ggray]

On my sail drive (Yanmar SD20) I can only pump out about 1/3 of the oil, so I pumped out what I could and replaced about 9 times. Got to be pretty quick about it!

But yes, I could hear a pressure differential when opening the cap, too, before I contrived a header tank.

[colemj]

Originally Posted by 2Hulls

I've also heard air when opening the dipstick - usually long after the last run since I check the oil right before the first daily start - but I don't know whether it's sucking or blowing - and I bet it doesn't have to be the same for each drive in each location. It's reasonable to expect that some heating takes place during operation and any air in the system expands, creating pressure. But whether this pressure dissipates or becomes a vacuum probably depends on the ambient conditions and the time between shutdown and opening the dip stick, e.g., it would be hard to believe that positive pressure would persist for a long time in cold water. The way to find out whether it's sucking or blowing would be to slop up the dip stick with soap bubbles and slowly crack it open. But either way, if there's either positive pressure or vacuum some time after the last run, that means the seals are holding something....

Dave

On ours, it is always a positive pressure, and it stays pressurized for a long time. I can open the dipstick after it has been sitting for a month after operation and the pressure releases. The water temp doesn't change much for us, but after opening it, it remains unpressurized until it is operated again. It then stays pressurized.

Mark

[Wanderlust]

I had not thought about the effects of the saildrive being pressurised until reading here.

So, if you check the fluid level after a long hard run and reseal it, I assume it will develop negative pressure as it cools. If the seals are good there should be no problem. But as they age the negative pressure may be sufficient to draw seawater in.

On that basis, I plan to always check levels when the drive is cool. Does that sound like good practice?

[ggray]

Lot of expansions/contractions to consider.

Oil and steel internal parts inside of an aluminum housing. All with different coefficients of thermal expansions.

Changing temperatures inside and outside over time.

The oil level is most likely always below the waterline, and oil is lighter than water.

So pressure differentials all over the place.

That's why I installed a header tank well above the waterline so there is always a slight pressure inside the sail drive.

[bighopper]

- How is this header tank connected? Is it above the top of the dip stick ????
- How do we dpressure test the saildrive? Can this be done without removing the drive from the block?
- Big Hopper - Wauquiez Pretorien "Sojourn"

[ggray]

I removed the "stick" out of the dip stick cap, and drilled a 1/4 inch hole all the way through it. Presses a 1/4 inch ss tube in the hole (tight fit because a hole drilled in stretchy materials usually relaxes when the drill is removed) so the bottom end was about at the full level. 1/4 inch tubing connecting this to a bottle I made and located about a foot or more above the water line. That gives it the slight pressure.

And I put a pinch valve on the tube to control the oil if the cap needed to be removed, which is hardly ever the case.