Separate thru-hull and line to stuffing box - SailNet Community
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post #1 of 16 Old 06-02-2005 Thread Starter
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Separate thru-hull and line to stuffing box

My dock neighbor has a Contest 34 built in Holland. Recently, a small thru-hull with a gate valve (I know, bad news) broke off. We plugged the hole but I wonder if he needs to restore the thru-hull. A hose from the gate valve leads to an opening in the stuffing box. Wouldn''t the box get enough water from around the shaft? Anyone heard of this arrangement?
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post #2 of 16 Old 06-03-2005
 
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Separate thru-hull and line to stuffing box

Some dripless stuffing boxes use a setup like you describe to lubricate the shaft. Since it is dripless the shaft gets no lubrication otherwise. If this is the case the stuffing box will quickly wear out and begin to leak potentially sinking the boat.
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Separate thru-hull and line to stuffing box

Wrong wrong wrong, the dripless stuffing boxes don''t get their lubrication from a seacock, they are submerged in water, how much more do they need? This sounds like a great way to sink the boat!

The dripless stuffing boxes need to be burped (like sailormitch after too many beers) of the air they sometimes trap, a hose leading from the stuffing box to above the water line (when the boat is healed) should do the trick. The things you read on the internet???
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Separate thru-hull and line to stuffing box

Denr,

I''m sorry but you are wrong wrong wrong. My Jeanneau has the type of dripless stuffing box you describe there are types that use a seperate feed line to lube the shaft. It''s a big world buddy and I don''t think you''ve seen it all yet.
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Separate thru-hull and line to stuffing box

This boat is probably 20 years old. Were dripless boxes availble back then? Also, I should have mentioned that the gate valve and thru hull originate under the water line about 2 feet from the shaft.

Any other thoughts?
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post #6 of 16 Old 06-03-2005 Thread Starter
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Separate thru-hull and line to stuffing box

This boat is probably 20 years old. Were dripless boxes availble back then? Also, I should have mentioned that the gate valve and thru hull originate under the water line about 2 feet from the shaft.

Any other thoughts?
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post #7 of 16 Old 06-05-2005
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Separate thru-hull and line to stuffing box

On dripless seals they need additional cooling only when used in high RPM powerboat applications.On sailboats most do not need to run an extra cooling tube to the seal because it will not overheat in that RPM range(probably because of no cavitation).
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Separate thru-hull and line to stuffing box

There is at least one dripless shaft seal for low RPM sailboats that does require a water feed for lubriction and/or cooling, namely "Strong Seal". I had one on my last boat and the yard mechanic used a "T" fitting from the engine cooling water discharge for the water supply to the shaft.
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post #9 of 16 Old 06-11-2005
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Separate thru-hull and line to stuffing box

JohnVT I just read up on these and I still cannot find a reason for this additional cooling hose.If the whole thing is submerged and there is not any cavitation or the hull leaping through the swells spinning the prop in the air.....I know it says to use this additional cooling hose however,they might be covering their butt to make it apply to all,so there cannot be problems of applying it to the wrong application.Well OK there are no 60 foot modern yachts with oarlocks.....That still is probably not safe to say.
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post #10 of 16 Old 06-13-2005
 
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Separate thru-hull and line to stuffing box

The extra water hose is not for "cooling" it is for lubrication to prevent heat build up. A dripless shaft seal must have a bearing surface that adhears tightly enough to the shaft to prevent water from entering. At this point there will be friction and then heat build up leading to failure. Some seals use a low frictiom teflon or carbon, some use a system that keeps a smal amount of water around the shaft and some use a seperate water circuit like the one in this post.
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