Tip on replacing a seal - SailNet Community
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post #1 of 5 Old 08-22-2009 Thread Starter
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Tip on replacing a seal

I replaced the rear seal on my transmission on this last haul out. I ran into some trouble with the installation of the new seal but came up with a pretty inexpensive tool to finally get-r-done.

The trick to driving in a new seal is to apply equal driving force on at least two more more sides of the seal simultaneously while pounding it in. With small seals, I usually can find a socket in the tool box around the same diameter and use that to drive in the new seal. This particular seal was four inches in diameter though and I didn't have an sockets that big. If you don't have anything protruding beyond the plane of the seal, you can just lay a block of wood over the seal and drive it in with a big hammer. I couldn't do this in my particular case, because the prop shaft coupler stuck out and was in the way.

I worked on it for a long time, tapping in one side and then trying to tap in the other side but each time the seal would pop out on the opposite side. It was getting frustrating. I solved the problem by going to home depot to the PVC pipe fitting section and looking at the all the different couplers and fittings until I found one with a diameter that was pretty close. Paid less than five bucks for it, took it to the boat, held it against the seal and laid a block of wood over the other end of the fitting and then drove it in. Took three ties and maybe five minutes instead of the hour or more I had already into it. Anyway, there is more than one way to skin a cat.

S.V. Nikko
1983 Fraser 41
La Conner, WA

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post #2 of 5 Old 08-22-2009
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Good tip, Ray. Thanks!

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post #3 of 5 Old 08-22-2009
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I just recently did the same job, had the same problem, different solution. While lying on my side trying to get the seal in with a hammer without damaging anything, it occured to me that metal expands or contracts pretty quickly with temperature. I thought of going ashore for ice to chill the seal. I didn't, but finaly got it level, though not seated. Next time I was aboard I put some crushed ice onto the collar, it rested against the top of the seal and dripped down it. After a few minutes I popped it in with a nail pry. Whatever tiny contraction the ice caused was sufficient. The same is true with heat, you don't need a torch to swell metal, boiling water will do.
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post #4 of 5 Old 08-22-2009
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yeah very good

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post #5 of 5 Old 08-24-2009
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Elastomer OD seals are designed for 10 to 30% compression of the elastomer to get a good seal without extrusion. This always makes installation interesting. Cooling the seal will shrink the case a little and stiffen the elastomer. NBR, viton and HNBR can be cooled to -30F without issue, not exceeding their glass transition temperature. Always preoil prior to installation. You're on the money to use an installation tool to apply force evenly on the case to prevent distortion. Any distortion on the case can transfer the uneven case shape to loading on the sealing lip. If severe enough reduce the loading between the lip and shaft to weep.

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