Shaft seal question

bob daily

bob daily

Well-known member
Joined
Aug 5, 2015
Messages
1,106
Fluid Motion Model
C-24 C SE
Hull Identification Number
2129K809
Vessel Name
Scuttlebutt
It is my understanding that only dripless shaft seals have a line going to the engine exhaust mixing system. It is also my understanding that Fluid Motions does not normally install the dripless shaft seals in there model's, as many owners have done this upgrade. After reading the post about hydrolocking of the engine after being towed and the question being why the factory doesn't inform owners of water entering via the shaft seal hose when the problem could be due to a owners modification?
I may be wrong with my understanding of the various shaft seals installed and please correct me if I am, but the question I have is the boats that have experienced the hydrolocking engine problems after being towed have a dripless shaft seal and if so, was it a aftermarket install?
Just curious Bob
 
DBSEA, Thank you for correcting me! Bob
 
Bob, the packing gland used by Fluid Motion is a Marine Hardware gland that has a water injection fitting in the gland. This water injection serves two purposes. (1) to help cool the packing gland and lubricate the packing while the engine is running and the shaft is turning. (2) to provide water lubrication to the cutlass bearing while the engine is running and shaft is turning. The reason this injection port is needed in this style inboard, the boat has a keel extension has a shaft log that houses the cutlass bearing. Water can not get to the packing or flow through the cutlass bearing when the boat is under way like it can in a traditional inboard with a open strut and open shaft log that is mounted to the bottom of the boat.

Yes, dripless packing seals also have water injection ports. This is to lubricate and cool the seal and also acts as a seal flush. There are probably more boats built today and in the past 20 years that the dripless seal is standard equipment. My 20 year old Mainiship Pilot has a Tides dripless seal installed on each shaft log and has a injection port that comes from the engine in the same way the Ranger and Cutwater Boats. The engines in the Mainship are mounted higher above the water line when compared to the engine in my Cutwater. I recently talked to a service tech at Tides when I ordered new seals and hose for the glands in my boat. Because the injection port installation of the Tides is similar to the injection port installation of the Marine Hardware gland installed in the Ranger and Cutwater. I asked him if they have issues of water backing up the water hose and ingesting water into the exhaust when a boat is being towed. He had never heard of that being an issue but it could be possible if the engine sits low enough in the boat. If that was the case, he thought the boat builder would address the issue when using this type of seal. This has never been an issue that he has heard of. He did say there could be a possibility of damage to the seal without water if the shaft was turning to fast while under tow and could also damage the reverse gear if the engine was not running. This he thought was common knowledge.

I believe if this was a common issue. With so many boats having water lubricated seals and packing glands installed in boats with the engines raw water cooling lubricating them it would be a known issue and all Towboat captains would be aware of it. I believe it would be a good idea to notify the Tow boat captains of this concern when towing a Ranger or Cutwater. Knowledge of the issue and a few simple steps to prevent the water ingestion could save a lot of money and grief to the boat owner. Me personally , I'm not convinced it is just the packing point. I would be looking at the combination of the exhaust outlet installation and the packing. Just my opinion.
 
Great discussion guys , so would the safe thing to do in all cases to close the raw water thru hull when being towed?
 
After looking at my Yanmar installation, I don't see how just towing at a reasonable speed could flood the exhaust/engine. I don't know the Volvo design so I can't speak for those boats. But since I essentially have towed the boat with my trolling motor for hundreds of hours with an open seacock and have seen no sign of water intrusion past the exhaust elbow I would conclude the design is sound.
However, I have experienced a vacuum on the multiport strainer while flushing the toilet with the boat on the trailer, seacock closed and wash down isolated. I would assume vacuum would also occur if I ran the wash down with the seacock closed but I haven't observed this. In this instance, if the boat was in the water then water would be sucked up the exhaust and shaft cooling hoses. IMHO I think a separate seacock for the engine would be a better design so that the house water works can be used with the engine water works isolated.
 
Firepara,

The answer to your question about shutting the sea cock if you are going to be towed with the engine not running is: YES absolutely. In June of 2018, I gained this knowledge the hard way while taking my R 27C from Seattle to Seward, AK. About 100 miles south of Prince Rupert, BC I had a mechanical problem unrelated to the hydro locking which required a 12 hour tow into Prince Rupert for repair. I did not have the common knowledge that the sea cock should be closed when towing. Upon arrival in Prince Rupert, my engine was hydro locked and required pulling the injectors to get the water out of the engine and turbo. The situation was corrected immediately and the engine has run fine since.

I spoke with Andrew Custis about the event after arriving in Alaska and requested that the operating manuals that FM create and supply has no mention about this important fact and that a 'WARNING' should be included. His response was that they cover this in the new boat delivery training and it is common sense that everyone knows about this. Of course this does no good for second or third owners and I believe there is no such thing as common sense, only COMMON KNOWLEDGE. So, through this forum we are trying to help people get this knowledge.

I'll make this request of FM once more. Please include a WARNING STATEMENT in your manuals that cover the inboards about what to do when towing an unpowered boat. And if/when you edit your manuals, put a note out on this forum that they have been updated so owners can download the latest edition. A side note, the Volvo manual makes no mention of this either or locking the reverse gear.

I created a small 4"X6" red warning tag which is permanently hung on the sea cock stating something like" Close sea cock when towing unpowered" to help me and potential future owners avoid this expensive mistake.

In following this forum, there have been a number of other boats that have hydro locked their engines while being towed, so this problem is systemic and not a 'one of'.

Stay safe.
Bob Allan
2016 R 27C 'Annie M'
 
I'll add on to this post since it is about the shaft seal. We have a 2016 C-26. The water injection hose fitting on the dripless shaft seal has broken. I'm in need of a source of supply for a replacement.
 
I would suggest determining which dripless seal you have and then contact the manufacturer. However, if it is a standard threaded barbed fitting, you should be able to screw it out and get a replacement at West Marine or other marine supply place. A dowel in the hole while searching will prevent water from running in.
 
Firepara,

I can tell you thru experience that closing the engine raw water intake is necessary but not sufficient in some Ranger Tugs/Cutwaters if you are being towed. If you search this site, you will find owners that had their boat towed with the raw water intake closed and still wound up with water in the engine. Some Liquid Motion boats have marginal engine installations.

I wish the factory would provide guidance on towing their boats. As the older inboards age the chances of a tow increase and more owners may experience a repower of their boat as I have. If it happens to you, expect a minimum $40,000 bill for the smaller inboards.
 
koedding@comcast.net":2jz6g07w said:
I'll add on to this post since it is about the shaft seal. We have a 2016 C-26. The water injection hose fitting on the dripless shaft seal has broken. I'm in need of a source of supply for a replacement.
Click to expand...

The gland is made by Marine Hardware give them a call 425-883-0651 they will be able to tell you the head size. I believe the hose ID is 3/8 and I think the thread size of the fitting is 3/8 NPT. Call them to confirm.
 
Brian,
Thank you! I was confused about shaft seal and it is not dripless.
Bruce
 
Thanks Brian!
I found the catalogue at their website and you confirmed what I found. Just need to confirm the size and find a source for the water injection fitting. West Marine had them in brass. But I know you can't mix brass with bronze. Per the website, it says its a brass stuffing box. So I should be good to go if West Marine stocks the correct size.
 
I would not advise using brass fittings for seawater use. It will break down with limited longevity. The stuffing boxes are usually made of a bronze material. In the case of marine Hardware ,Cast red bronze. I would confirm with Marine hardware what metal fitting to use and thread size.
 
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