A Hose of Surprise

[roetter]

Today I wanted to flush the saltwater out of the heat exchanger for the winter layup. As I prepared one of the hoses to suck fresh water from of a bucket I got a wet surprise, a big crack in the hose (see picture). This part of the hose is connected to the intake of the sea-water pump. The location of the crack is a good distance below the waterline. I had a little bit of water under the engine for some time. However, I had suspected the high pressure side hoses, after the pump, to have maybe pinhole leaks, and had replaced these two hose sections a few weeks ago with a black rubber marine hose.



Today, by accident I discovered this crack. In my laziness I had also started to leave the sea-water intake open during the season, as I had once destroyed an impeller because I forgot to open the intake before starting the engine. My boat could have sunk right on the dock this winter.

This hose was unchanged from the factory installation. It was well routed and well supported. The boat, a Bavaria Vision 40, is just 5 years old.

In my opinion, the wire in the hose does nothing to make it better, but actually introduces internal cracks that can grow bigger with just the vibrations caused by the engine. I will replace all hoses of this type with a black marine rubber variety.

I had a small pinhole about 3 years ago in the pressure side of the sea-water cooling system. But since I thought it had been accidentally punctured, I replaced it with the same style hose.

Has anyone else had failures of this type of hose?

[delmarrey]

This is why the USCG and ABYC recommend a heavy double walled w/wire reinforcement to be used below the waterline. As well it should be double clamped.
A Trident #100 or 250 series is the norm.

[Emmalina]

looks to me like it was clamped to a different size tube or double clamped without enough tube under it causung a stretch.... I use this hose for everything and never had a failure in 30 years...

[HopCar]

I think that type of hose is usually used for bilge pump discharge above the waterline.

Always try to avoid using hose with wire in it. The wire will rust and cause the hose to fail much sooner than a similar hose with out wire. Of course sometimes you have to use hose with wire (hard wall) if you have to make a tight bend or a long run on the suction side.

Trident 200 series is a good quality soft wall hose for your application.
Trident Ply Marine Wet Exhaust Hoses -SOFTWALL Mfg# 200

If you must use a wire reinforced hose try the Trident 250 series.
Trident Flex Marine Wet Exhaust Hoses -HARDWALL Mfg# 250

[roetter]

Originally Posted by delmarrey

... As well it should be double clamped. ...

As you can see from the picture it was double clamped.

[roetter]

Originally Posted by Emmalina

looks to me like it was clamped to a different size tube or double clamped without enough tube under it causung a stretch.... I use this hose for everything and never had a failure in 30 years...

It was on the proper size tube and installed by the factory. I don't know what you mean by "enough tube under it". If you are referring to the length of hose on the tube, this can be easily judged by the double clamping visible on the left side. It had about two inches on the tube. The end of the tube has a rounded edge.

[roetter]

Originally Posted by HopCar

...
Always try to avoid using hose with wire in it. The wire will rust and cause the hose to fail much sooner than a similar hose with out wire. Of course sometimes you have to use hose with wire (hard wall) if you have to make a tight bend or a long run on the suction side.
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My thinking. The wire is the cause of the problem. Thinking back, the first leak occurred at a wire too. The wire was rusted almost one full way around. In this case you can also see the rust along the wire. The expansion of the rust furthers the crack growth.

[sailorchic34]

Originally Posted by roetter

It was on the proper size tube and installed by the factory. I don't know what you mean by "enough tube under it". If you are referring to the length of hose on the tube, this can be easily judged by the double clamping visible on the left side. It had about two inches on the tube. The end of the tube has a rounded edge.

The second hose clamp was tighten to a smaller diameter then the first one, which can sometimes be an indication that the clamp was not sitting completely over the pipe stub that the hose slipped over.

I have several hoses where the pipe stub is not long enough to bear fully with two hose clamps. There I just make sure that I use a single new all stainless hose clamp, tightened with a socket and check it every so often. As the second one can cause the hose to split sometimes if its not bearing fully on the pipe below the hose..



Really a pretty lucky find in any case.

[monte]

Like sailorchic said, it looks like the outer hoseclamp was completely off the pipe and squashing it and causing a point to cut. What do you think? Either way, lucky to find it! A good reason to haul on the hard for winter!
How is the L450 progressing, is it delivered yet?

[gonesail]

i would replace all hoses like that with the heavy duty black rubber USCG approved variety. you will not have any more problems after that.

[Rakuflames]

Originally Posted by roetter

Today I wanted to flush the saltwater out of the heat exchanger for the winter layup. As I prepared one of the hoses to suck fresh water from of a bucket I got a wet surprise, a big crack in the hose (see picture). This part of the hose is connected to the intake of the sea-water pump. The location of the crack is a good distance below the waterline. I had a little bit of water under the engine for some time. However, I had suspected the high pressure side hoses, after the pump, to have maybe pinhole leaks, and had replaced these two hose sections a few weeks ago with a black rubber marine hose.

Attachment 68582

Today, by accident I discovered this crack. In my laziness I had also started to leave the sea-water intake open during the season, as I had once destroyed an impeller because I forgot to open the intake before starting the engine. My boat could have sunk right on the dock this winter.

This hose was unchanged from the factory installation. It was well routed and well supported. The boat, a Bavaria Vision 40, is just 5 years old.

In my opinion, the wire in the hose does nothing to make it better, but actually introduces internal cracks that can grow bigger with just the vibrations caused by the engine. I will replace all hoses of this type with a black marine rubber variety.

I had a small pinhole about 3 years ago in the pressure side of the sea-water cooling system. But since I thought it had been accidentally punctured, I replaced it with the same style hose.

Has anyone else had failures of this type of hose?

I don't know if it was that kind of hose, but we've had two intake hoses crack in the club marina in the last couple of months. Both times members spotted that the boat was sinking. They could prevent it in one case but not the other. My hoses are not clear. They're heavy black. After the first near-sinking I checked all my hoses and found that although the fellow who installed the new engine was overall really, really good, he had accidentally NOT used marine grade clamps on the water intake hose. 18 months after installation, two of the four were so rusted through that they broke into several pieces during removal. Oops.

Doesn't matter how good the hose is if it falls off!

[thinwater]

The reason for the wire in this style hose is not strength but rather to prevent collapse under vacuum. Since this hose is on the suction side of the pump you would be ill advised to go with non-suction rated hose. Thought there would not normally be any significant suction, obstruction by growth or trash could change that, even a good non-suction rated rubber hose collapse, and the engine overheat.

Sanitation hoses (white PVC) accomplish vacuum resistance through stiffness. But they can only withstand vacuum cold and over ~120 F will collapse in a heartbeat under serious vacuum. A very poor choise for engine compartment. No one suggested that, of course.

The reason the hose failed was not wire; it failed because the hose was a poor design for this use... or perhaps any use. Wire should never be used without fabric belts providing additional strength, pressure resistance, and spreading the forces generated around the wire.

[roetter]

Originally Posted by monte

Like sailorchic said, it looks like the outer hoseclamp was completely off the pipe and squashing it and causing a point to cut. What do you think? Either way, lucky to find it! A good reason to haul on the hard for winter!
How is the L450 progressing, is it delivered yet?

If you look closely at the picture you will see little proud ring to the right of the last clamp. This is the rounded berm at the end of the pipe (see Volvo sample picture). The second hose clamp was definitely fully on the pipe. I am wondering if the second clamp was tightened so much, that the wire in the hose was forced over this berm in such a way that it cut through the wall to the inside. The water ingress than started to corrode the wire and that led to the crack.
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Monte, she is on her way. Left Les Sables yesterday. Got the first satellite position this morning. I was over there a week ago to check her out. She is a pretty girl.

[roetter]

Originally Posted by gonesail

i would replace all hoses like that with the heavy duty black rubber USCG approved variety. you will not have any more problems after that.

Thanks, That is exactly what I am doing. Just one more hose of this type left at the head intake.

[hellosailor]

As thinwater said, wire hose is designed to prevent hoses from collapsing under suction. That's standard practice and the wires don't ordinarily cause any problem. I wouldn't replace it with "plain" hose, just take some care with the choice and installation of the new hose. That vinyl (?) hose looks thin compared to conventional wire-reinforced rubber hoses, it could just be that piece was defective, too thin to properly retain the wire in it. These days? I wouldn't be surprised to find defective chewing gum.