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Old 24-04-2008, 11:04   #16
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Hey Sully,

Lower seals aren't a big deal but I still wouldn't try it without the boat hauled. There are a few things that can go wrong and commonly have. First the allen head bolt holding the prop can break if it gets stubborn. Secondly the splined shaft has a tendency to crack at the outer threads of the allen bolt if too much pressure is applied. If the prop comes off easy it's just a matter of pulling the zinc then I believe another four bolts to pull the lower gear. If you are talking the main seal replacement here's the tough part. That seal needs to be pressed off then of course pressed back on, no big deal if you carry that kind of press equipment around. Trying this especially for the first time at low tide doesn't make sense to me even if you have that kind of tide where you are. My boat draws 3'6" from the water line to the bottom of the sail drive give or take a few inches. Then you have to be a bit lower than that to both put a bucket under the drive to drain the oil and to have easy work access to the seal. I'd assume if you could find an area that it could be done in it would be right at slack time just as the tides starting to return, that's some pretty close timing even if all goes as planned. If you're seeing any kind of cloudy color in your SD20 oil, first thing I would try at low tide is to drain the oil from the drain plug below the hub. Here's the most important part, repalce that O-ring. From what I've learned many times people fail to do this and just screw in the plug with the old O-ring and 50% of the time the water getting into the sail drive is from a bad O-ring and not the main seal. Might be worth a try.
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Old 24-04-2008, 11:14   #17
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Hey Sundog,

I figured it was an Athena. Mines a 95. If you do get this boat let me know I'd love to trade tips with you. This is the first Cat I've had and though she's a bit older and I've done a lot of work on her (needed and upgrades) I keep being amazed at how much easier she is to work on than my other monos.
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Old 24-04-2008, 11:17   #18
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Hey Sully,

Lower seals aren't a big deal but I still wouldn't try it without the boat hauled. There are a few things that can go wrong and commonly have. First the allen head bolt holding the prop can break if it gets stubborn. Secondly the splined shaft has a tendency to crack at the outer threads of the allen bolt if too much pressure is applied. If the prop comes off easy it's just a matter of pulling the zinc then I believe another four bolts to pull the lower gear. If you are talking the main seal replacement here's the tough part. That seal needs to be pressed off then of course pressed back on, no big deal if you carry that kind of press equipment around. Trying this especially for the first time at low tide doesn't make sense to me even if you have that kind of tide where you are. My boat draws 3'6" from the water line to the bottom of the sail drive give or take a few inches. Then you have to be a bit lower than that to both put a bucket under the drive to drain the oil and to have easy work access to the seal. I'd assume if you could find an area that it could be done in it would be right at slack time just as the tides starting to return, that's some pretty close timing even if all goes as planned. If you're seeing any kind of cloudy color in your SD20 oil, first thing I would try at low tide is to drain the oil from the drain plug below the hub. Here's the most important part, repalce that O-ring. From what I've learned many times people fail to do this and just screw in the plug with the old O-ring and 50% of the time the water getting into the sail drive is from a bad O-ring and not the main seal. Might be worth a try.
I'll give that o-ring idea a try in a couple hours when she comes out of the water.

Oddly, the saildrive oil is turning lighter AND I'm getting pressure in there. If the filler cap isn't on all the way, the oil will rise up and overflow eventually (over weeks). If the filler cap is on snugly, it will go "pffft!" when you open it and release built up pressure.
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Old 24-04-2008, 12:28   #19
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Oddly, the saildrive oil is turning lighter AND I'm getting pressure in there. If the filler cap isn't on all the way, the oil will rise up and overflow eventually (over weeks). If the filler cap is on snugly, it will go "pffft!" when you open it and release built up pressure.

I get the small pressure thing too. But I did notice that before and after I did the main seals. You'd think with a positive pressure like that, water wouldn't be coming in. Also I read that when you check oil levels on the SD you are supposed to do it with the cap just sitting on top of the fill hole not by screwing it in to get an accurate reading but it seems every engine I own has a different rule for that from my lawnmower to the boat. My SD 20 manuel doesn't say I just read it on Diesel.com
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Old 24-04-2008, 12:34   #20
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Sulli,

I am at work, and will look for the diagrams tonight on the boat. I would imagine the pffft comes from expansion when the system is hot. I noticed the same thing before, and after the seals were done too..................
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Old 24-04-2008, 13:04   #21
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If the oil color is getting lighter it could mean your mixing water with the oil. Ive seen this happen with mine, I have a leaky lower seal caused by fishing line and nets being caught in the prop.
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Old 24-04-2008, 13:50   #22
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Sulli,

I am at work, and will look for the diagrams tonight on the boat. I would imagine the pffft comes from expansion when the system is hot. I noticed the same thing before, and after the seals were done too..................
Duh!!! ha ha

Of course! I can't believe I wasn't thinking of that one. The monotony of singlehanding a couple thousand miles will do that to you. Kind of makes you dumb...

Ram, yes, I am definitely getting water in. That's why the gear oil is lightening up. I have to put a stop to that water. Looking at the seals today, while I scrape some barnacles and look at the possible removal of prop cages. Waiting another 1/2 hour for the tide.
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Old 24-04-2008, 14:33   #23
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I think there is a bit of confusion on this thread regarding seals. Some seem to be talking about the rubber seal that seals the hole in the boat the drive leg passes through and keeps the water out of the boat. This is a double seal on the Yanmar and a single seal on the Volvo. Yanmar recommends replacing this seal every two years and Volvo recommends every seven years. This replacement is much more complicated and I sure wouldn't attempt it between tides. The engine needs to be unbolted, moved forward and the saildrive removed from the boat. This is definitely a job that needs to be done correctly and if you get the timing wrong or run into problems, the consequences are pretty bad.

The other seals being discussed are the shaft lip seals that keep water out of the saildrive oil (and saildrive oil out of the water). To get to these, you remove the prop, undo two machine screws and the casing holding the seals comes right off. Well, pretty easily at least. Some people whack the little casing "ears" to turn the casing sideways and then whack them from behind to persuade the casing off. The casing fits into the saildrive with two o-rings providing the seal, so there really isn't much friction holding it on. I just replaced these seals last weekend and since I don't like whacking on my saildrives, I made a little puller out of a couple of long bolts and a scrap of aluminum. The seals themselves are typical lip seals like you find in pumps, etc. They are pressed in and can take a bit of persuasion to get out. Whether one can do it between tides is probably more of a measure of how much experience one has changing these types of seals and how prepared one is in advance.

If the main boot seal was leaking it will allow water into the boat and I would get the boat pulled pretty quickly and replace it. That one is critical.

A leaking lip seal will show up as water in the saildrive oil and will turn the oil cloudy and milky. This isn't as critical and I would pull the boat to change it at a convenient time. My lip seals are 10 years old and still perfect. I just decided to change them this year as a matter of course. Now they will require replacement every year with my luck.

Mark
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Old 24-04-2008, 14:37   #24
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Never mind. I didn't see that this was a two page thread and responded after only reading the first page. I now see that everyone is talking about the lip seals holding water out of the saildrive.
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Old 24-04-2008, 14:39   #25
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Forgot to mention that mine is a Volvo drive. I only have the two back-to-back lip seals on the shaft like is found in water pumps and don't have a pressed on main seal.
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Old 24-04-2008, 16:07   #26
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Still good info, Mark.

With your post and some mucking around (literally) under the boat this afternoon, I am getting a better understanding.

I pulled the props, put on a zinc, and put back together. This allowed me to get so far as to see the next thing behind the props on the shaft... this little collar that just sits there loosely, with nothing holding it in place. Does everyone have this thing?? It's got a hole in it so it is slid onto the prop shaft, and basically it just sits there doing nothing between the prop and the body of the saildrive. It doesn't appear to be attached or sealed in any way. Maybe the tension of the prop is what keeps it in place?
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Old 24-04-2008, 16:55   #27
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Apparently, you can change the lower seals while the boat is still in the water. I found this thread.. HERE

The fella is very convincing. It's amazing what you can find in the nooks and crannies around here!!
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Old 24-04-2008, 18:43   #28
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Check out this link. Friendship Eerder verschenen
It describes seal change procedure. Also, Boatworks magazine did an excellent description with photos. I will try to find the issue but maybe a year ago.
If you have rebuilt pumps, bearings seals it should be doable.
Hope this helps
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Old 24-04-2008, 18:49   #29
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That little collar does need to be there. I don't recall at the moment why and what it is called but it just sits in there. The Volvo has this also. It may be some type of water deflector. Possibly to keep water under pressure from the spinning prop away from the seal? That just popped into my head.
When I did mine the seal housing was a bit eaten up by electrolysis so I replaced it with a new one. The seal was separate so I used a C-clamp and a large socket to press it in place. Lessen:watch your zincs. I think getting the old seal out may be the hardest part. Check the price on a new seal housing. It may be worthwhile to keep one on hand with a seal in place to make the change out quicker in the future.
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Old 25-04-2008, 06:34   #30
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Sulli,

If some one can accept a fax, and then e-mail you the blow up I have it. I don't have a scanner working. I am in the shop working, but will check every so often to see what's up......
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