Raw water vented loop, hose type required

[elliot_russo]

Hi,

I have new beta 75, all below waterline and will be replacing short hose from hx to mixing elbow with a vented loop. Total length around 5m (15'). ID is 25mm (1") What type of hose is required, what sort of temperature water can I expect, and how hot will barbs get.

Any thoughts on valve vs small hose to cockpit (or similar) on the vent? Valve is much easier for me.

[rbk]

I use Trident 110 or 100 (or similar reinforced engine hose). https://tridentmarine.com/product-ca.../engine-water/
Reason being they live in the engine compartment and are subjected to high temps, oils, fuels ect. Don't cheap out as your raw water hose if compromised WILL sink your boat if unattended.

[tkeithlu]

QUOTE: "Don't cheap out as your raw water hose if compromised WILL sink your boat if unattended."

This needs particular emphasis. Think of the walls of this hose as being part of your outside hull. Make it easy to close this seacock in a hurry while sinking. Use fuel hose. Use two really good clamps on both ends.

[Shrew]

Originally Posted by tkeithlu

[B] Use two really good clamps on both ends.

I'll double-down on this statement.

1) I use two hose clamps anywhere under the waterline, or anywhere I absolutely DO NOT want a failure. (e.g. bilge pump discharge, sanitation lines).

2) For critical jobs I use heavy-duty, non-perforated hose clamps. The entirety of a perforated worm gear hose clamps is holding with the two tiny straps of metal on the sides of the perforations. Take a good look at a perforated hose clamp and look at how much metal is actually holding that clamp together. I've found these broken in the bilge on several occasions.

[Niall leslie]

I'd suggest CG rated marine engine reinforced coolant hose with 2 heavy duty SS hose clamps at each joint. Check all regularly and replace each 5-10 years or earlier depending on use and condition since cool fresh water in the Great Lakes is very different from hot salt water in the tropics.
I'd also recommend exercising the seacock every month as part of the routine maintenance checks.

3 decades in the maintenance end of the industry.

Good luck and enjoy.

[chasmains]

I’m a strong proponent of good technical practices and hose clamps are included in this. Broken worm-drive hose clamps are often broken because they are over-torqued. And most people do that. All industrial grade clamps have torque specs. You should observe torque specs ALWAYS for below waterline installations. Take this one for example: https://www.mcmaster.com/5415K33. Max Torque is 25 inch-pounds. I’m fine with double clamps. But why over-torque them and dare the connection to come apart out on the water? McMaster-Carr has torque screwdrivers but they are well over $100. So that makes them out of range for most. Amazon has a 10-70 in-lb unit for $30.

[sinnerman]

Originally Posted by Niall leslie

I'd suggest CG rated marine engine reinforced coolant hose with 2 heavy duty SS hose clamps at each joint. Check all regularly and replace each 5-10 years or earlier depending on use and condition since cool fresh water in the Great Lakes is very different from hot salt water in the tropics.
I'd also recommend exercising the seacock every month as part of the routine maintenance checks.

3 decades in the maintenance end of the industry.

Good luck and enjoy.

Same for the FUEL lines. Many boats use auto parts store fuel lines which are not rated for marine use. (Heat, fire resistance...)

Not cheap, but quality comes with a price.

cheers.

[Cheechako]

Originally Posted by elliot_russo

Hi,

I have new beta 75, all below waterline and will be replacing short hose from hx to mixing elbow with a vented loop. Total length around 5m (15'). ID is 25mm (1") What type of hose is required, what sort of temperature water can I expect, and how hot will barbs get.

Any thoughts on valve vs small hose to cockpit (or similar) on the vent? Valve is much easier for me.

When you say "how hot will barbs get?" I fear you are considering non metal barbs. DON'T!
Can you find a 1" vented loop? Not sure I have seen that. Don't go down in size. The problem with vented loops is the cheap valve on the top, so I'm a fan of valve elimination if you can.

Being a modern engine I suspect it runs fairly hot? 190-200 degrees F?

I tried to use the big USCG rated fuel line once. The 3/8" hose was maybe 7/8- 1" OD! It could not be clamped with normal clamps and stay on a brass barb fitting as it didn't compress. Slid right off with clamp as tight as possible. Abandoned that.

[Nord Sal]

A small hose to the cockpit or elsewhere is preferable to a vented loop. Simplicity! No moving parts to fail! If you can see it discharging, you'll know it isn't blocked.

[FPNC]

Raw water temp will only be between 5-10 degrees higher than the sea water temp. Even though raw water cooling water temps are low, use an exhaust quality hose that has a wire core to prevent any chance of kinking. Either a plastic or metal vented loop will work. It is important to use a vented loop that does not restrict water flow. I.E., the same size as the engine fittings. Either a valve or small hose will work. A valve is a maintenance item. A small hose not so much and verifies operation of the loop.