View Full Version : Marine Hose Selection
So the other day I needed to remove the lenth of hose which runs from the seacock on my boat to the sea water strainer to gain access to the raw water pump impeller behind it. The whole sea water system from seacock to strainer to hydraulic cooler to raw water pump on the engine is 2" marine wet exhaust hose and due to its rigidity, the only way I could remove that one section without dismantling the whole system was to cut it out with a hacksaw. The builder must have had to use a pipe bender to use this hose in areas where there's substantial bends.
Anyway, now I need to replace it. I'm wondering if using this type of hose for this application is overkill and if there's a more flexible, easier to work with hose available. Last night while at a Lowe's store I noticed that they sell a white flexible PCV hose that appears to be quite substantial yet much more flexible than the marine exhaust hose. It doesn't have the wire reinforcement, but resisted my body weight to crushing. Now, I typically dismiss any product sold at these stores for use in marine applications (especially below the waterline) but I was intrigued by this hose and wondered if it is, in fact, a suitable product for sea water intake.
1) Has anyone used this flexible PVC hose for this application?
2) Is this even advisable, or something to stay far away from?
3) Could this same hose be used for the sanitation hose from my head to holding tank to overboard seacock (here again, the builder used marine exhaust hose which seems an expensive option)?
01-03-2011, 08:04 AM
price the liquidtight non metallic grey electrical conduit at an electric supply house.
that is a waterproof grey pvc type hose and is tough wont crush and typically cheap.
01-03-2011, 08:10 AM
I'd NOT use shorebrand PVC !
I'm wondering if he used 2" exhaust hose because 2" intake hose was hard to find - most sourses show 1-1/" though you can get 2" from Edson and from the more industrial marine houses. Intake hose, like exhaust, has wire wound in it to prevent the collapse of the walls under the suck of the pump.
2" ?!?!?! Still having trouble getting my mind around this but I guess as something inline before the strainer it's ok. I'd consider getting the strainer closer since it only needs to be above the waterline for cleaning.
Anyway, the exhaust hose might be your only option. Exhaust hose is resistant to heat but is still a bit more ductile when warm. It's probably a bit long to immerse in hot water - unless you have a spa at home - but get it as warm by air and maybe pouring boiling water into one end, the other being plugged, just before you head out for the horror show.
01-03-2011, 10:51 AM
Don't even think about using a non marine rated hose... Besides the reasons Ian mentioned your insurance policy would be void when your boat sinks. I would go with the reinforced exhaust hose that was originally installed.
01-03-2011, 11:15 AM
Replace with the same hose. Its heat and collapse resistant and, after all, is all that stands between bilge and sea (until you throw the seacock lever anyway)
I've pre-bent such stiff hoses using weights, clamps and, depending upon length, shoving a piece of rebar in them longer than the hose and using the protruding ends like levers to induce a bend. As Ian stated, heat will help you in the prebend or bend-in-place operation.
01-03-2011, 12:00 PM
As it's under suction, you want a wire-reinforced hose, but you don't need the heat resistance of an exhaust hose. Shields makes a wire reinforced rubber hose for engine water applications. It's less obstinate than exhaust hose. Can't remember the number. It might have been called Shieldsflex.
I'd NOT use shorebrand PVC !
2" ?!?!?! Still having trouble getting my mind around this but I guess as something inline before the strainer it's ok.
I'm wondering why you're questioning 2" hose, is that not a common size?
You had me at: "when your boat sinks" and "insurace company" references.
I think I'll drive past Lowe's on my way to Defender and compare their 2" marine exhaust hoses, both with and without wire reinforcment. They call the unreinforced hose "Soft exhaust hose" and claim it won't collapse. If this feels adequately strong against collapse and feels easier to work with, I'll try that. If not, I like the idea of warming up the wire reinforced stuff for ease of installation.
Thanks for the responses,
01-05-2011, 10:13 AM
I've only limited experience working around engines - sail auxillaries all under 30 hp, one summer as captain of a vintage motor yacht with a couple of big old diesels but we had a real engineer for that, and my time on tugs where again the engineer kept us going so long as I paid sufficient homage and recognized the natural tension between the deck and engineering departments.
But if you peruse the catalogs, 1-1/2" suction hose is about the largest common size. I have to go through real work to get 2" for my big Edson. And the amount of water needed for cooling a small diesel really does not take that big a hose. So either it's a bigger engine than I'm used to or the builder wanted a big pipe from cock to strainer, perhaps as a prophylactic against suffering from sucked in garbage bags or something.
Edited to add: As I push my memory back thirty years to that classic motor yacht - the seacocks to the intake strainers may well have been 2", but the strainers were right on top of the cocks so there was no hose run there. I seem to remember that the hose out of the strainer was more like an inch. I presume there is some reason, like no space or access, that CJ's boat has this hose length. And I'd be interested to know what the hose is from the strainer to the pump.
01-05-2011, 12:26 PM
exhaust hose" and claim it won't collapse.
Pull some off the roll and replicate the bend it needs to make in the boat. Look at the bend for collapse.
01-05-2011, 12:34 PM
It seems wrong that you have to cut the hose or dismantle the whole mess to remove an impeller.
...the natural tension between the deck and engineering departments.
And I'd be interested to know what the hose is from the strainer to the pump.
In my case, the engine is a 370 hp Yanmar. From the seacock to the engine mounted pump inlet, it's all 2". Including in & out of the strainer and a hydraulic shell & tube heat exchanger. It makes a pretty severe bend where it enters the pump and must have been fun to install that section.
I agree with Mr. Williamson that this shouldn't be run right in front of the pump, thus making it impossible to get at the impeller without removing the hose and I may try to reroute it there. However, Yanmar doesn't make it easy to get to that impeller even if the engine were hauled out of the boat, so I tolerate the hose issue. The section I removed was a 3 foot piece between the seacock and strainer and since they're both hard mounted and the hose was a straight shot (and cold and stiff) I couldn't pull it off in either direction - the sawzall made the job much easier.
As for the natural tension between deck & engine - been there, I understand...
01-06-2011, 01:26 AM
SP, Lest you are not convinced, forget Home Depot hose, this needs to be wired marine engine water hose, but does not have to be exhaust hose, there is a hose that has the barest hint of a corregated type shape that can make these runs and bends better. And it also may be it is time to improve the plumbing, perhaps an elbow or 45 in the run will make servicing easier...Cheers, BT
The fastest and sometimes the only way to remove an old hose is to cut it off.
Fresh hose is more flexible than old and easier to fit, even if it' s reinforced. Pre-forming with heat can help, as mentioned above. An electric heat gun is a big help for softening hoses. I don't bother with boiling water anymore.
Sounds funny, but water-based personal lube products from the drug store can also help overcome a tight fit over a hose bib. Working in a boat often means working in cramped spaces where there is little room to get leverage from your arms and hands. I use whatever helps.
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