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Separate thru-hull and line to stuffing box

4K views 15 replies 5 participants last post by  dman 
#1 ·
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?
 
#3 ·
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???
 
#7 ·
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).
 
#9 ·
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.
 
#10 ·
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.
 
#14 ·
Denr you are wrong on this one. PSS I''m not even sure that PSS still sells the "non-vented" Shaft Seals that you MUST burp (I had one on my old boat) All the ones that I see PYI sell all have a "vent tube" to ensure water gets into the seal as they have had very rare but occasional failure due to overheating of the seal and some scary failures.

They now have you put a small hose on the Shaft Seal and run it at least 2 feet above to water line to ensure that there is no air in the shaft seal, But there really is no nead to connect to a thru hull unless it was a high speed boat

Look at the directions here (specifically item #9 in diagram and instruction #15)

http://www.pyiinc.com/images/pdf/PSSInstructions.pdf
 
#16 ·
On the pss system this vent would make perfect sense.Why anyone would go out of their way to install the "strong seal" on a sailboat is beyond me.That hose that comes off is force fed water as was mentioned earlier.I could just see something getting into that hose blocking it or some other probem like a raw water pump falure to have a real mess on your hands.I`m sure someone will endorse it for a sailboat and I would be curious to know why.
 
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