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Old 08-07-2020, 01:35 PM   #1
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Hose clamps failure can sink a boat

One day I took my boat out for a short ride with several friends and at the end of the trip I ran it up to full WOT as I do at least once a month to check the performance and temperatures. This time I had a huge surprise when alarms went off and scared all the guests. My alarm panel reported high temperature on one engine, but I shut down both. I threw out an anchor and made a quick trip to the engine room. I have snap-disc sensors at the exhaust on each engine which report three levels of high temperature. On this occasion it was Code Red! The problem was a raw water hose from the pump that had slipped off the pipe into the engine cooling system. The engine room was a hot mess and after it had cooled down enough to inspect the hose I saw it was a broken hose clamp and the break was on the back of the pipe where it was hard to see and get to. It had corrosion which I had overlooked. It was a quick fix since I keep a good supply of replacement hose clamps onboard and a good time to discuss this subject.

As simple as they are, hose clamps are critical to marine engines, and are prone to breaking and corrosion. Everybody knows to buy stainless, but often it is only the band, but not the screw. Take a magnet when you go shopping. There are two levels of stainless. 304 alloy is medium and okay for most applications, and 316 is the best and should be used in wet areas like the shaft log. Since hose clamps were invented and patented in Europe they retain their sizes in metric making it a little more difficult to choose. You can mark your spares in inches if you wish, but there is a tendency to buy oversize, which produces tails with sharp edges and corners waiting to cut your hands. There are hose clamp tail-guards available called Hose Clamp-Aids available at Amazon. You can also use wire heat shrink.

A major difference is the way the perforated thread is made. Initially they were all perforated and this was a major weakness and where corrosion usually starts and was cause for over tightening, too. They are now available embossed Ė a big improvement.

In addition to the standard hose clamp design, there are two more. One is the Constant Tension, which is most often used with fiberglass pipe where the pipe size changes due to changes in temperature. These have an internal spring which prevents crushing. The second type is the T-bar clamp, which is available in longer and wider sizes and are stronger. These are for larger connections and they also have protruding bolts that can snag clothes and cut hands. Shrink wrap works well here, too.

Now letís look at tightening hole clamps because it is important, they are easy to over or under tighten. There is such a thing as a torque screwdriver A Full size clamp is generally torqued to around 30 to 50 inch-pounds lbs. (1/12th of a foot pound). Beware of perforated bands which are weakened by the holes and stretching them invites corrosion. Marine hose clamps normally have both a slotted head and a hex head. A large enough screwdriver for the necessary torque is often difficult to get to the screwhead and mor difficult to feel the pressure applied. I much prefer a ľ inch socket wrench with a magnetic socket drive to prevent lost drivers which full under the engine. You can adjust the torque by holding the wrench close to or away from the clamp and you have the choice of a right angle or straight connection depending upon the adapters. I also use a small battery powered screwdriver like the Apollp with a Two-position pivoting handle for access to tight places and speeds up the process. A flexible screwdriver can also be very helpful in difficult to reach places.
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Old 08-07-2020, 02:06 PM   #2
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Only if it’s connected to the sea water through hull.

When we leave the boat for a few hours I close the valve.
Many don’t. I didn’t for years.
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Old 08-07-2020, 02:08 PM   #3
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Regardless of all that, all raw water hoses must be double clamped just for this reason. Sounds like yours are not.

You may want to go back through the ER and double check the others.
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Old 08-07-2020, 02:15 PM   #4
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AWAB clamps.
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Old 08-07-2020, 02:20 PM   #5
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Good clamps and double clamped whenever the barb allows. And situations like this are why alarms are good and bilge pumps should be sized to keep up with a failure of the largest underwater fitting. Then if a failure happens somewhere, it'll make a mess, but you'll know about it quickly and the boat won't be at significant risk from it.
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Old 08-07-2020, 02:42 PM   #6
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The exposed 'tail' of the tightened hose clamp can easily be trimmed with a tin snips
and the sharp edge dressed with a stone or a grinder.
The exposed stud of a T-bar clamp can be cut off with a hacksaw or dremel and likewise
dressed.

I do this (hopefully) before they draw blood but always afterward!
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Old 08-07-2020, 02:50 PM   #7
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Quote:
Originally Posted by rslifkin View Post
Good clamps and double clamped whenever the barb allows.
.
And so often they are not
Especially if using wider T Bolt type clamps

Quote:
And situations like this are why alarms are good and bilge pumps should be sized to keep up with a failure of the largest underwater fitting. Then if a failure happens somewhere, it'll make a mess, but you'll know about it quickly and the boat won't be at significant risk from it
Yep, we have 4 x 3500gph at varying levels,
Counter on the lowest and alarms on the highest
And 2 x 240v trash pumps that can be brought on line at the flick of a switch.
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Old 08-07-2020, 02:52 PM   #8
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Like a friend of mine who is a professional very experienced mariner told me one day, "un paquet de bateaux ont coules par les chiottes", meaning a whole bunch of boat sank from the toilets

L
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Old 08-07-2020, 05:06 PM   #9
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Another strong vote for the AWAB or Skanvik clamps. Those fully perforated clamps are junk. I went through my boat and methodically eliminated them. In the process I found many that had essentially failed already. You have to be very careful with Tbolt and constant torque clamps, a torque wrench and a knowledge of the torque spec of the fitting the hose is being attached to are important. Here's an expensive example of over-tightening exhaust hose to fiberglass muffler. We installed crush rings to mitigate that ever happening again.





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Old 08-07-2020, 05:18 PM   #10
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I used some AWAB T bolt clamps on my exhaust and stuffing box this winter. I am really impressed with the quality and how heavy they are. Also no welding but rather an interlocking system.
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Old 08-07-2020, 06:45 PM   #11
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While we’re on the subject of hose clamps, what about hoses? How long is too long before replacement? Engine hours, years, both?
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Old 08-07-2020, 06:50 PM   #12
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I think about 10 years.
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Old 08-07-2020, 08:51 PM   #13
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If your hose shows cracks in the outer skin you might think about replacing it.

If your hose becomes pregnant or has a soft spot you might think about replacing it.

If the end of your hose is showing signs of delaminating you might think about replacing it.

If your hose is twenty years old you might think about replacing it.
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Old 08-07-2020, 09:12 PM   #14
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Mike, nice to see you posting! I always enjoyed your Grand Banks comments, photos and how-to's.
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Old 08-07-2020, 09:21 PM   #15
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I use AWAB hose clamps X 2 and if a barb doesn't allow double clamping, exchange for a longer barb fitting.

I use "T" handle torque wrenches for tightning hose clamps and check critical hose clamp torque once a year. I loosen the hose clamp before torquing.

As for clamp tails, I have a good assortment of clamps in various sizes to reduce the length of tails. And I place an AWAB Hose Clamp Tail Tip Cover on every clamp. Why go through the effort of heat shrinking or cutting the tail when cover are inexpensive, easily fitted, looks good and is the correct solution.

For T-Bolt clamps, I slip Clamp Aids over the protruding bolt.
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Old 08-08-2020, 08:12 AM   #16
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Steve D'Antonio Hose Clamps Part I: Design and Selection

Steve D'Antonio Hose Clamps Part II: Installation and Use

On the hoses, replace by age from date of manufacture not years or hrs of service. 12 yrs is the # I got from a port engineer I used to work for. Sooner if any sign of weakness tiltrider1 lists in post #13. The hoses I can reasonably reach get a wiggle and squeeze test while performing routine maintenance. On one installation I had a hose the for unknown reasons was prone to early failure so it got the wiggle and squeeze test prior to every cruise.

And don't forget convenience hoses. The PO bless his heart installed a reverso oil change system. But the hose he used is low quality and has hardened. Oil change is coming up and those hoses and clamps will all be renewed. If I loose one of those hoses I loose all the oil in the pan, engine damage before the alarm goes off is very likely.
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Old 08-08-2020, 12:57 PM   #17
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Double hose clamps

I appreciate the feed back and the opportunity for dialogue. I do use double hose clamps on connections under the water line IF there is enough space. I don't in other locations for several reasons. First, ABYC does not recommend double clamps, except at below the water line. Second, there is often not enough room for two clamps side by side. Most importantly I don't because it makes removing the hose all the more difficult and it usually stretches the hose and can even result in poking a hole in the hose. The hose that slipped off in my story was the connection to my cooling system's acid wash and is removed at least once a year and often more. I was at fault for failing to check this hose clamp and test it for strength. This hose is not below the waterline and is only in use when the engine is running and I am on the boat. If the seawater pump is not working water can't get past the pump. The alarm did its job perfectly.
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Old 08-12-2020, 01:28 PM   #18
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Snap Disc Temperature Alarms

This is in answer to a personal email asking "What is a snap disc temperature alarm?". These are stainless normally-open sensors about the size of a fat quarter that close when the termprerture to which they are attached reaches a specific temperature. I use three of them at the exhaust pipe on each engine tied on with heavy duty wire ties. These are wired to Super Bright LEDs on the instrument panel and the The first one is set to the normal cruising temperature and connectded to a green LED. The second is set for 15 degrees higher connected to a yellow LED and the third at 20 degrees higher has a red LED. The highest temperature snap disk is also wired to a solenoid which is connected to a very loud bell. Snap discs come in a variety of temperatures, but are in celius degrees. Each snap disc has male spade terminals. They cannot be attached with adhesive which will reduce the sensitivity.

The advantages are that they give immediate reports and the lower termpeatre ones indicate a cooling system that is in need of cleaning. The parts are inexpensive and easy to get, Super bright LEDs are just what the name implies, but also require a small resister to lower the 12 volt source.
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Old 08-22-2020, 10:19 AM   #19
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Great Information

I just want to say thank you to everyone who posts these great answers and provides such helpful information. About 20 years ago I started buying old RWD Volvo cars and was always impressed with the embossed hose clamps they used. The AWAB looks even better.

Knowledge like this is so important. I wonder how people afford a boat like these without mechanical knowledge, or at least interest. I feel so much better after getting the Hawks' Nest home and spending afternoons just looking at the mechanic of it and tracing stuff down.

I am struggling to convince myself to close all of the sea cocks when I leave the boat for just a few days.

Thanks,

Steve
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Old 08-22-2020, 10:40 AM   #20
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Originally Posted by Hawkshaw1 View Post

I am struggling to convince myself to close all of the sea cocks when I leave the boat for just a few days.

Thanks,

Steve
I don't close the two seacocks on Sandpiper or previous boat when I leave the boat. Have not had a leak or sinking in 35 years. I go to the boat a minimum of once a week and conduct a bilge check.

I did replace both seacocks, hoses and clamps shortly after boat purchase. Hoses and clamps were replaced again at 15 years. I loosen and retorque the critical hose clamps every spring and replace ones that look iffy.

I do close the two seacocks if we are out of town over a week. In addition, I close the 8 seacocks that are installed on all the thru hulls above the waterline when out of town.
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