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Old 06-19-2017, 05:55 AM   #1
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Stuffing box water line

There are water lines on our boat injecting raw water from the engine exhaust to the stuffing box/cutlass bearing tubes for each shaft. I've been told they are to help prevent crevice corrosion and/or to ensure a water flow through cutlass bearings that are embedded in these shaft housings.

The aft half of each water line is copper (3/8" ID, I believe) and the rest is reinforced potable water hose. One of the copper tubes froze and burst over the winter and I'm planning on replacing both of them. The burst is near the sharp bend in the photo.

Does anyone have a system like this and have you ever replaced the copper with something like PEX? Whatever I use, the bend will have to be kink-proof.

Thanks.
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Old 06-19-2017, 06:08 AM   #2
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My dripless stuffing box has the same type of setup. I just ran 3/8" heavy duty rubber marine fuel hose. I check it annually for pliability. Probably wouldn't use PEX at the engine because of vibration.

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Old 06-19-2017, 06:08 AM   #3
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Yes and mine is just reinforced water hose from water injection elbow to barb fitting on stuffing box.

They won't prevent crevice corrosion on the shafts if they sit for long periods without running the engine unless you are pumping water through them all the time by a different method.

I have read that some do the extra pump method....I havent done it yet...if ever.
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Old 06-19-2017, 07:25 AM   #4
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Mine is set up like post #2.
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Old 06-19-2017, 07:31 AM   #5
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Thanks, guys.

My stuffing boxes aren't dripless so I've never been sure what the exact purpose of these lines from is. Also, they originate from the underside of antisiphon fittings that someone installed previously.

These lines have the potential to allow a lot of water in if they fail. Have either of you considered adding ball valves at the stuffing box to serve as seacocks?
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Old 06-19-2017, 07:45 AM   #6
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Where does the water pressure come from for the injector, the raw water engine pump?
if so, having a manifold splitting off pressure means it would be easy to stop the flow. Pex is not going to kink and it does bend. A reinforced rubber hose I think is better. Can you buy small diameter with wire reinforcement?

I replaced my 5/8 fuel line vent hose with the USCG approved stuff. Has a nylon liner and that stuff won't kink because it is really thick and was cheap cost of $3.40 per foot. Similar would be smaller USCG approved fuel line hose with the smooth nylon liner.
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Old 06-19-2017, 11:56 AM   #7
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My stuffing box looks about the same. When I got the boat it had some legacy copper tubing abandoned in place, but it was no longer hooked up and capped off. I've left it as such.

Pex and/or heavy duty fuel line would be my choice if I was going to hook it up back up
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Old 06-19-2017, 12:35 PM   #8
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Ours looks similar, heavy duty hose between exit of gear oil cooler and stuffing box. It has to ensure water flow through the bearing which would otherwise be limited to the leakage of your stuffing box.
What are the two green hoses on your stuffing box? We have only one hose from the engine room.

You're right there is a potential of water coming in if the hose between stuffing box and engine fails. We experienced it once when we had to get a gear out while in the water and disconnected the hose at the gear oil cooler ...
But due to the small diameter of the hose the amount of water could be easily controlled by the bilge pumps in case of failure.
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Old 06-19-2017, 01:57 PM   #9
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To answer a couple questions, the water pressure originates at the raw water pump. The two green wires are part of the bonding system. I'm leaning toward some kind of reinforced, non-kinking hose. Thnx.
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Old 06-19-2017, 03:08 PM   #10
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The water injection is to prevent the possibility of the stuffing box running dry while under way.

I've never seen it be an issue in a slow speed boat. So you could abandon it and cap it off.

Especially if you repack with GFO packing.
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Old 06-19-2017, 04:46 PM   #11
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Capt. Bill,
I'm not a naval architect and my thoughts might be incorrect:
The injection is located between stuffing box and bearing. Most of the injected water will flow via the bearing outside IMO. Why? The amount of water which flowed inside when we disconnected the hose at the gear oil cooler was significantly higher than any stuffing box leakage we ever encountered. My conclusion on that was that the bearing clearances seem to be higher than those from the stuffing (although or bearing doesn't have excessive clearances out of tolerance).
Of course the injected water has a a certain quench effect for the stuffing but will it really prevent the stuffing from running dry if it is set too tight?
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Old 06-19-2017, 07:48 PM   #12
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Quote:
Originally Posted by waddenkruiser View Post
Capt. Bill,
I'm not a naval architect and my thoughts might be incorrect:
The injection is located between stuffing box and bearing. Most of the injected water will flow via the bearing outside IMO. Why? The amount of water which flowed inside when we disconnected the hose at the gear oil cooler was significantly higher than any stuffing box leakage we ever encountered. My conclusion on that was that the bearing clearances seem to be higher than those from the stuffing (although or bearing doesn't have excessive clearances out of tolerance).
Of course the injected water has a a certain quench effect for the stuffing but will it really prevent the stuffing from running dry if it is set too tight?
I had similar thoughts. The bearings in question (at least on my boat) are cutless bearings located at the extreme forward end of the shafts. They are effectively in "tunnels" formed by the hull and the angle of the shaft penetration. I assumed that they don't get much water flow up there and the lines are intended to irrigate them, as waddenkruiser notes.

I am going to contact Wilson Lin in Taiwan, who builds Defevers, and ask about them. I'll post whatever I hear back.
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Old 06-19-2017, 08:26 PM   #13
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You are correct and I guess I should have given a more detailed explanation.

The injected water would push out around the bearing, if there is one.

But even in installations with a bearing I've never seen a issue with the bearing if there is no injected water. Many stuffing boxes don't have a water injection fitting at all.

And again I'm speaking about slow speed vessels with slower turning shafts.

I have also serviced boxes where it's obvious the injection fitting is so corroded and plugged up that there has been no water going into it for a long time. And it shows no apparent ill effects.

And this is just my opinion after a long time servicing these types of systems.
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Old 06-19-2017, 09:19 PM   #14
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Quote:
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You are correct and I guess I should have given a more detailed explanation.

The injected water would push out around the bearing, if there is one.

But even in installations with a bearing I've never seen a issue with the bearing if there is no injected water. Many stuffing boxes don't have a water injection fitting at all.

And again I'm speaking about slow speed vessels with slower turning shafts.

I have also serviced boxes where it's obvious the injection fitting is so corroded and plugged up that there has been no water going into it for a long time. And it shows no apparent ill effects.

And this is just my opinion after a long time servicing these types of systems.
That's good to know, Capt.Bill. If they serve no purpose, I wouldn't mind losing them.
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Old 06-19-2017, 09:23 PM   #15
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Greetings,
Mr. 99. Not to dispute Mr. 11's comments, but there must have been SOME use and reason for installing them in the first place or they wouldn't be there. If it were me, I would restore original use with rubber tubing as others have done.
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Old 06-19-2017, 09:53 PM   #16
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Water doesn't naturally flow up the bearing toward the stuffing box. The lines are there to ensure water for lubrication of the bearing and to provide minimum cooling. Some shaft setups have a scoop built into the hull that forces water continually with forward motion.
It also helps flush out marine organisms. The higher temperature isn't their best growing condition.
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Old 06-19-2017, 11:09 PM   #17
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I'm thinking the green hoses are grounding cables??
Edit - I didn't refresh and see the new responses...

Quote:
Originally Posted by waddenkruiser View Post
Ours looks similar, heavy duty hose between exit of gear oil cooler and stuffing box. It has to ensure water flow through the bearing which would otherwise be limited to the leakage of your stuffing box.
What are the two green hoses on your stuffing box? We have only one hose from the engine room.

You're right there is a potential of water coming in if the hose between stuffing box and engine fails. We experienced it once when we had to get a gear out while in the water and disconnected the hose at the gear oil cooler ...
But due to the small diameter of the hose the amount of water could be easily controlled by the bilge pumps in case of failure.
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Old 06-19-2017, 11:55 PM   #18
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Quote:
Originally Posted by Lepke View Post
Water doesn't naturally flow up the bearing toward the stuffing box. The lines are there to ensure water for lubrication of the bearing and to provide minimum cooling. Some shaft setups have a scoop built into the hull that forces water continually with forward motion.
It also helps flush out marine organisms. The higher temperature isn't their best growing condition.
What higher temperature?
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Old 06-20-2017, 05:49 AM   #19
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"Whatever I use, the bend will have to be kink-proof. "

A spring bender is quite cheap , a better one for tighter turns is at any refrigeration supply.
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Old 06-20-2017, 10:09 AM   #20
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My boat is keel-cooled and does not have any water injection into the stuffing box. The boat was built in 1975.
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