What does the hose on the stuffing box do?

[YukonRon]

We have a 2016 R29 with the Volvo Penta D4-260. We just had the stuffing box re-packed while hauled out for painting, and found the threads were messed up, so it had to be replaced. The yard put in a new stuffing box that does not have the barb fitting to attach the small hose that comes down from the back of the engine. The hose was left dangling in the bilge.
What does this hose do? Am I missing an important function without having it attached to the stuffing box?

 

[4umfreak]

Water is supposed to pass in through the cutlass bearing around the prop shaft and out the hose. It keeps the cutlass from getting hot and wearing prematurely.
I don't know enough to know why your would be without the hose barb.

 

[YukonRon]

Water is supposed to pass in through the cutlass bearing around the prop shaft and out the hose. It keeps the cutlass from getting hot and wearing prematurely.
I don't know enough to know why your would be without the hose barb.

I always maintain a drip of several drops per minute from the stuffing box. I thought that was enough flow to keep the seal and bearing cooled and lubricated. Is that not enough? Should there be a steady flow out the hose? I assume then that the flow up the hose would be going out with the wet exhaust?

 

[YukonRon]

I should add that the mechanic came out on a sea trial to adjust the new stuffing box. He left it dripping steady at more than once per second while running. On the way home I measured it with the temp gun at 30 degrees C. When I stopped, it still drips at the same steady rate. That will give my bilge pump a steady workout. He told me I can tighten it up after 4 to 5 hours break-in time. Does this sound reasonable? I'm hoping it will settle in and cool down after break-in. I will be going back to the yard after the long weekend with questions; but hoping to get info here first. Thanks in advance.

 

[NorthernFocus]

Water is supposed to pass in through the cutlass bearing around the prop shaft and out the hose. It keeps the cutlass from getting hot and wearing prematurely.
I don't know enough to know why your would be without the hose barb.

This is backwards of most. Typically the hose comes off the cooling water circuit. The intent is to flush and cool the packing. On older boats this wasn't done and apparently the stuffing box used per the OP is of this older design. Not wrong just different. But need to plug the now loose hose or will get continuous flow to the bilge.

 

[NorthernFocus]

I should add that the mechanic came out on a sea trial to adjust the new stuffing box. He left it dripping steady at more than once per second while running. On the way home I measured it with the temp gun at 30 degrees C. When I stopped, it still drips at the same steady rate. That will give my bilge pump a steady workout. He told me I can tighten it up after 4 to 5 hours break-in time. Does this sound reasonable? I'm hoping it will settle in and cool down after break-in. I will be going back to the yard after the long weekend with questions; but hoping to get info here first. Thanks in advance.

You measured what at 30C? Shaft? Stuffing box gland? What's water temperature in your area? Sometimes you can have TMI. Slow drip. If shaft is slinging water it's too loose. No drip or you see steam it's too tight. Anywhere between is a matter of preference.

 

[YukonRon]

This is backwards of most. Typically the hose comes off the cooling water circuit. The intent is to flush and cool the packing. On older boats this wasn't done and apparently the stuffing box used per the OP is of this older design. Not wrong just different. But need to plug the now loose hose or will get continuous flow to the bilge.

From my research I'm starting to understand that the hose provides water flow from the engine raw water / intercooler circuit through the packing gland/stuffing box to cool the cutlass bearing. Is that correct?
The loose hose has been plugged with a bolt inserted and a hose clamp.

 

[YukonRon]

You measured what at 30C? Shaft? Stuffing box gland? What's water temperature in your area? Sometimes you can have TMI. Slow drip. If shaft is slinging water it's too loose. No drip or you see steam it's too tight. Anywhere between is a matter of preference.

I measured 30 C at the body of the stuffing box gland, while cruising at 7 knots, with water dripping more than once per second. Ambient sea temp is about 13 degrees C.
Water continued to drip at the same rate when parked. This is way too much for a stationary boat, but I'm reluctant to tighten it in case it runs hotter.
Not sure if things will improve with break-in when I get to run it some more, or will I be overheating the packing?

 

[4umfreak]

Yeah, I thought it flowed in, but it sounds like it flows out! Also, some discussion if it's still required with modern stuffing materials! Given that your new stuffing box doesn't have it, maybe its ok!

I had it disconnected once and water came trickling up the hose!

 

[YukonRon]

Yeah, I thought it flowed in, but it sounds like it flows out! Also, some discussion if it's still required with modern stuffing materials! Given that your new stuffing box doesn't have it, maybe its ok!

I had it disconnected once and water came trickling up the hose!

Are you saying the water flowed OUT of the gland fitting and up the hose toward the engine? was this with the boat moving and engine running? or at standstill?

 

[fishheadbarandgrill]

On my 2011 R29, a hose runs from the exhaust elbow to a nipple on the top of the stuffing box. at higher RPMs (above 1000), water flows from the exhaust elbow into the stuffing box.

 

[NorthernFocus]

From my research I'm starting to understand that the hose provides water flow from the engine raw water / intercooler circuit through the packing gland/stuffing box to cool the cutlass bearing. Is that correct?
The loose hose has been plugged with a bolt inserted and a hose clamp.

It's mainly to cool and lubricate the packing. Same design used on pumps in various applications.

 

[NorthernFocus]

I measured 30 C at the body of the stuffing box gland, while cruising at 7 knots, with water dripping more than once per second. Ambient sea temp is about 13 degrees C.
Water continued to drip at the same rate when parked. This is way too much for a stationary boat, but I'm reluctant to tighten it in case it runs hotter.
Not sure if things will improve with break-in when I get to run it some more, or will I be overheating the packing?

You're way too worried about it. Water will boil before packing is damaged. As long as you have a slow drip it's fine. Once per second is a bit much. For your own knowledge you can tighten it a bit at a time and monitor temps.

 

[4umfreak]

Are you saying the water flowed OUT of the gland fitting and up the hose toward the engine? was this with the boat moving and engine running? or at standstill?

Engine not running, was in the slip.

 

[YukonRon]

You're way too worried about it. Water will boil before packing is damaged. As long as you have a slow drip it's fine. Once per second is a bit much. For your own knowledge you can tighten it a bit at a time and monitor temps.

That's what I originally assumed also. But on reading further there is lots of expert recommendations that a cutlass bearing installed inside a prop shaft log needs water injection to insure a constant cooling. It is not guaranteed a steady water flow in a semi-planing boat the way a cutlass bearing would out on a strut behind a sail boat.
Would Fluid Motion install the cooling hose if it can be disconnected and ignored? I'd like to hear from the factory on that.

 

[YukonRon]

Update: The boat yard that did the stuffing box replacement has agreed that the water injection hose and the attachment point for the bonding wire (both missing on the replacement stuffing box they installed) are both required items as designed by the factory. As such they have ordered the correct replacement parts. It does mean we have to go through the process of getting the boat to the yard and back again, but they will do the work at no extra cost.
Mistakes happen, and the fact that they immediately owned up to it and took the initiative to make it right is the mark of a good service provider.

 

[4umfreak]

Update: The boat yard that did the stuffing box replacement has agreed that the water injection hose and the attachment point for the bonding wire (both missing on the replacement stuffing box they installed) are both required items as designed by the factory. As such they have ordered the correct replacement parts. It does mean we have to go through the process of getting the boat to the yard and back again, but they will do the work at no extra cost.
Mistakes happen, and the fact that they immediately owned up to it and took the initiative to make it right is the mark of a good service provider.

Yay! ...and that's how you keep a customer coming back!