Stuffing Box Water Injection

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meridian

Guru
Joined
Aug 21, 2011
Messages
1,014
Location
USA
Vessel Name
Meridian
Vessel Make
Krogen-42
My stuffing box has water injection and over the years I have seen many other boats that had none. When is water injection required? If I didn’t need it I could clean up some of the engine plumbing.
 
It is needed if the design of the shaft tunnel or the arrangement of the cutless bearings in the shaft tunnel are such that insufficient cooling and lubricating water can get to the cutless bearings and shaft log when the boat is moving forward. If your boat has a water feed to the shaft log(s)--as ours does--it has it for a reason. Removing it will cause the shaft log(s) to overheat severely and fast and extreme damage to the log and possibly even the shaft will result.
 
My 40 albin also has water feed. 6 years ago when I bought it the original copper tubing was still in place and in good shape. I changed it to hose the year I bought it when I installed the dripless packing.
The water feed is simple and carefree. I wouldn't eliminate it.
 
If you have an IR hand held temp monitor use it to see what your packing temperature is.

I sugggest you keep your water feed no matter what type of packing you have.
 
I believe the water injection is for higher speed boats. It certainly won't do any harm by leaving it in. IIRC 10 kts and above was the point at which it was necessary.
 
Also the water injection feeds, in my case anyway, from the heat exchanger and thus provides a normalization temp to the packing - especially in colder water environs where some packing might harden. I agree with all - leave it be.
 
I believe the water injection is for higher speed boats. It certainly won't do any harm by leaving it in. IIRC 10 kts and above was the point at which it was necessary.

SF: I think your right about the speed. The amount of water that gets back to the shaft log isn't much but I have to go with the manufacturer. They designed, built and installed it as part of the system. I'm keeping ours. :)
 

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Water injection is present for different stuffing boxes becsause of boat design AND speed.

On a trawler single where the stuffing box is at the end of a long shaft log (some cases over 10 foot ) it's there so there is some water movement (also note that's a great reason to pump oxygenated water in there (every few days?) so your stainless shaft doesn't start rusting.

Where the shaft log isn't long but on slower vessels...sometimes there's no water injection but even PSS seals now has a tube as an air burper so the drip less seal doesn't ever get air bound. On planing vessels the water injection is there in case cavitation happens and air bubbles start to fill that void where the shaft comes through the hull.

For PSS seals, you can freewheel a dead engine as long as you go under 10 knots or so as water still finds its way in to cool the seal...but over that and you better have cross water injection or lock the shaft.
 
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