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Old 05-11-2020, 04:11 PM   #1
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Dripless shaft seal flow meter. Good or bad idea?

The boat came with full flow meters and needle valves on the water feed for the dripless shaft seals. Great in theory but I'm thinking over engineered. One of the flow meters failed last time out. The failure was the indicator stuck "down" so no water flow to the shaft seal. This could have caused the shaft seal to burn up. So I'm thinking of removing the flow meters and needle valves.

I'm asking for opinions on using flow meters on the shaft seal water feed. How many have flow indication of any kind on your dripless seals? Seems like overkill to me. I'm new to dripless always having had old fashioned stuffing boxes in the past.
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Old 05-11-2020, 04:15 PM   #2
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I think that is way over engineered. It is another point of failure. I have an alarm on the exhaust hose right after the mixer. If I loose water flow it will go off. If I have water flow through the engine then I should have flow into the dripless seal. Too much over thinking IMO.
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Old 05-11-2020, 04:31 PM   #3
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K.I.S.S I don't mean to be offensive but why oh why do some guys overcomplicate things.
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Old 05-11-2020, 04:44 PM   #4
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Thanks for your opinions. I'm in agreement, they will be removed. I'll look into a temp alarm on the exhaust hose.

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I think that is way over engineered. It is another point of failure. I have an alarm on the exhaust hose right after the mixer. If I loose water flow it will go off. If I have water flow through the engine then I should have flow into the dripless seal. Too much over thinking IMO.
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K.I.S.S I don't mean to be offensive but why oh why do some guys overcomplicate things.

Irish, you're not offending me. Wasn't my over complication.
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Old 05-11-2020, 04:58 PM   #5
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Look at Borel Manufacturing. I have their alarms on the exhaust, high water and water in fuel. Easy install and draws no power unless there is an alarm. No affiliation just a very satisfied customer.
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Old 05-11-2020, 05:09 PM   #6
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+1 on Borel. Aqualarm makes one too, but the Borel alarms at a lower temp, therefore giving a bit earlier warning.
Even with the exhaust hose alarm, there is a remote possibility that your water line to the shaft seal could stop flow, and the exhaust hose would not overheat if the main flow continued. Personally, I don't worry about that at all.
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Old 05-11-2020, 05:24 PM   #7
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I'm real low tech Portage Bay.
Seawater filter blocked = higher engine temps (monitored ritually as part of constant awareness) + louder engine noise.
Speedseal means I need to get the filter cleaned asap but with a little safety margin.
Bottom line is ?
Far less electronics/wiring/connections/sensors and things to go tits up when you really need them = we keep all basic human sensors fully activated.
We've just got a different approach, some of you love electronics then if you enjoy it, then go for it.
I'm just an old fashioned luddite, I study the weather patterns, use paper charts (backed up with GPS) and basic sailors instinct.
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Old 05-11-2020, 05:28 PM   #8
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I've had dripless water fed seals on two boats probably 16 or 17 years in total. I never had an issue with water blockage. I check them in the fall when I haul out, and feel the feed hose every now and again during the season.
Plus I'm always checking water flow at the exhaust outlet.
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Old 05-11-2020, 05:37 PM   #9
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I've had dripless water fed seals on two boats probably 16 or 17 years in total. I never had an issue with water blockage. I check them in the fall when I haul out, and feel the feed hose every now and again during the season.
Plus I'm always checking water flow at the exhaust outlet.
On my last boat the water feed for the dripless shaft seals used substandard plastic hose and plastic barbed fittings. They were not secured and I actually broke one of these while being typically clumsy in the engine room. I considered that a lucky break and replaced with reinforced hose and proper connections and secured all hose runs.
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Old 05-11-2020, 05:51 PM   #10
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Hello,
I notice that most shaft seals are connected to the exit end of the cooling sea water circuit. on my boat the water feed to the shaft seals is connected to the water intake end . Any thoughts whether this functions just as good or not ? Up to now I never had any issues but than I`ve only had the boat for a year .
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Old 05-11-2020, 06:02 PM   #11
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Hello,
I notice that most shaft seals are connected to the exit end of the cooling sea water circuit. on my boat the water feed to the shaft seals is connected to the water intake end . Any thoughts whether this functions just as good or not ? Up to now I never had any issues but than I`ve only had the boat for a year .
How does that work? If it is hooked to the intake end isnít that suction? Maybe a photo will help explain it.
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Old 05-11-2020, 06:02 PM   #12
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Portage, I agree that the needle valve / flow meter concept is an accident waiting to happen and it's overworking the potential problem of coolant water not getting to the seals. What I do in my hourly ER checks is touch the water entry point on the seal with a finger to make sure it's cold.
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Old 05-11-2020, 06:21 PM   #13
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How does that work?
If it is hooked to the intake end isn’t that suction?
I guess it's on the intake side, but after the raw water pump.

Regardless, in principle engine manufacturers recommend to not "steal" raw water to the engine cooling system, neither upstream nor downstream of the engine coolers, because also the latter still reduces the cooling of wet exhausts.

That's the reason why some boats (mine included) are built with a third alternative, which is a specific raw water intake for each shaft seal.
Feeded only by the dynamic water flow with no pumps, but that's ok, since the heat to dissipate is proportional to the boat speed.
And very simple, with nothing that can possibly wrong, aside from some garbage getting stuck in the intake.

In this sense, I see the point of flow meters - which I don't have.
But all considered, yes, I also agree that it's an accident waiting to happen.
Unless maybe there is one sensor type which can only fail open, hence avoiding the risk that it's supposed to protect from.

Is anyone aware of such thing, maybe?
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Old 05-11-2020, 08:13 PM   #14
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I have drippless seal but checking the flow is not something I can do unless the boat is on the hard and I start it up, like when I winterize it. It seems like there is a lot of water going through it, like gallons an hour.

Does this sound about right?

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Old 05-11-2020, 10:53 PM   #15
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I have the Borel alarm that will tell me immediately if I loose water flow. I see no need for an alarm on the stuffing box water flow. I see mostly downside problems with the alarm.
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Old 05-12-2020, 06:08 AM   #16
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I have LOTS of experience with no flow to dripless seals.

Between assistance towboats in shallow water and the boats pulled off...hundreds of incidents. Plus all the Sea Ray's I ran for a dealership prior.

Usually you dont get blockages while running...its usually after a grounding where the narrower feed hoses pack up.

Some sort of telltale dribble or just checking it at first start and after any shallow water work should suffice to let you know of a problem.

Beyond that........paranoia about everything will keep you tied to the dock.

And yes there are other failure modes than plugging .....but good hoses and clamps, regular inspections and good old luck should keep them to a minimum.

Most people including my surveyor last friday say they have decades of trouble free operation with these seals.
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Old 05-12-2020, 06:08 AM   #17
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I think the risk is that the feed line to the shaft seal becomes plugged up, and I have heard of it happening. You would have plenty of flow through the exhaust, so no alarms, but a potentially melting shaft seal. I'd venture a guess that the previous owner had such a problem, and installed the flow meter to guard against it. I doubt he thought, "how can I complicate my boat further? Oh, I know..."


So keeping an eye on cooling water to your shaft seal, whether dripless or not, is important. Too little can cause overheating, and it can cause stagnation of the water and crevice corrosion.


I think the best way to monitor, and it's not perfect, is with a temp sensor on the shaft seal. A loss of water will show up as a rise in temp. If you don't have a temp sensor, then you should be periodically checking it by with a thermal gun.
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Old 05-12-2020, 06:36 AM   #18
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If you don't have a temp sensor, then you should be periodically checking it by with a thermal gun.
Agreed wholeheartedly.
Thermal gun is the greatest thing since sliced bread, and there's no replacement for occasional trips in the e/room with one of them.
Not just for shaft seals, obviously.
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Old 05-12-2020, 06:50 AM   #19
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I have drippless seal but checking the flow is not something I can do unless the boat is on the hard and I start it up, like when I winterize it. It seems like there is a lot of water going through it, like gallons an hour.

Does this sound about right?

pete
Pretty much what I do. I make sure there is pink antifreeze that came out of the cutlass after I winterize.
It's only a 1/4 or 3/16 ID hose.
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Old 05-12-2020, 07:33 AM   #20
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I think the best way to monitor, and it's not perfect, is with a temp sensor on the shaft seal. A loss of water will show up as a rise in temp. If you don't have a temp sensor, then you should be periodically checking it by with a thermal gun.
This! Our routine ER checks utilize a thermal gun reading at the shaft seal location.

Also, a failed coolant pump or hose will overheat engine with no indication on exhaust hose Borel alarm.
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