Raw water vented loop question

[smokey73]

Hunter 40.5 with a Yanmar 4JH2E 50HP.

I have a small drip from the vented loop in the raw water line to the Mixing Elbow. I cannot find this loop or the vent on the Yanmar 4JH2E parts manual. Does anyone know the part number for this vent valve?

 

[Davidasailor26]

It’s probably not a Yanmar part, just a random manufacturer. The one on our Beneteau with Yanmar engine is a Vetus.

 

[Rick D]

I replaced mine with a Vetus about 15 years ago.

 

[dlochner]

It is a generic vented loop, not a Yanmar Part. The vent sometimes gets plugged or loosens. Unscrew it, clean it up and test it. It should allow air to flow when you suck on it and stop air if you blow into it. If it is still good, reinstall it with some teflon tape on the threads.

The particular model you have is pretty hard to find, not a common brand for the big box stores. Here's one source:

Scot Pump - Vented Loops 316 Stainless Steel , Part No. 913-VL15

The 20013 Marine Vented Loop provides a proven way to break the vacuum in marine water systems. Bank siphonage will be broken if the loop is approximately two feet above water level. The Vacuum Breaker has a normally closed poppet which keeps vent line fumes from the vessel. The breaker is...

mmarineonline.com

They may also sell just the valve.

Other vented loops maybe more budget friendly if the one. you have must be replaced.

 

[smokey73]

Rick, I expect that it is just a "generic" part. I'm wondering what the size of the threaded fitting that fits into the loop itself. Any ideas of the size? I can't imagine it is too expensive.

 

[dlochner]

Rick, I expect that it is just a "generic" part. I'm wondering what the size of the threaded fitting that fits into the loop itself. Any ideas of the size? I can't imagine it is too expensive.

It was about $25 or $30 when I replaced mine in Key West.

 

[JamesG161]

What caused it to leak in the first place?

The plastic vent thread?

Rare event bothers me.

Jim...

 

[Ralph Johnstone]

What caused it to leak in the first place?

The #$%^&*> seat and/or plug in the crappy little plastic valve. The first and only time mine leaked, it leaked salt water down the side of the engine. Had to take every fitting and component off the starboard side of the engine in order to thoroughly clean and then paint the side of the engine.

After is was cleaned up and I was so PO'd thinking about if it were to happen again, I decided to run a small, clear vinyl hose from the cooling water thru-hull to the engine and see how I was for water level and the mixing elbow. "Viola," the sea water level was 6" below the level of the middle of the mixing elbow so "screw it", out with the leaky syphon breaker.

I know the ABYC recommends an 8" clearance for no vac. breaker but there is no way I can see building up enough head to flood the exhaust hose, muffler, and exhaust header when under sail. Throw in the resistance of a positive displacement raw water pump and it further reduces the problem.

 

[smokey73]

Interesting @Ralph Johnstone . I know the mixing elbow is above the waterline. I'll have to check the exact waterline level on my boat.

Since this is really only a problem when sailing does it make a difference if the boat is heeled? Does the ABYC standard mean 8" above the fully loaded heeled waterline or the static waterline at a light load? I was inspecting the hoses and clamps and that is when I saw the moisture. My mixing elbow is not exactly on the centerline so if I'm on a Port Tack, it will be closer to the waterline than if on a Stbd Tack. Maybe I'm overthinking this.

Guess this might get flagged when it comes to selling the boat as a Survey item?

 

[dlochner]

Interesting @Ralph Johnstone . I know the mixing elbow is above the waterline. I'll have to check the exact waterline level on my boat.

Since this is really only a problem when sailing does it make a difference if the boat is heeled? Does the ABYC standard mean 8" above the fully loaded heeled waterline or the static waterline at a light load? I was inspecting the hoses and clamps and that is when I saw the moisture. My mixing elbow is not exactly on the centerline so if I'm on a Port Tack, it will be closer to the waterline than if on a Stbd Tack. Maybe I'm overthinking this.

Guess this might get flagged when it comes to selling the boat as a Survey item?

As you note there is a difference between the static waterline and the dynamic waterline. If the engineers at Hunter thought the loop was necessary, I don't know I would go second guessing them. I have the same vented loop, when mine started leaking I removed it, tested it, and put it back in. 300 or 400 motoring hours later it doesn't leak. If yours leaks and tightening the valve doesn't work, then purchase a nice Vetus or Groco loop for under $100.

 

[sailcapt340]

As Dave stated Scot is the part you want. Mine looked liked yours and replaced it a while back. The plastic vent broke off from the rusting.
Sorry, This is the best photo I have of the repair but you have the right source for yours now. You can zoom in on the photo and see the name.
An easy enough job to get back to normal.

 

[JamesG161]

I know the ABYC recommends an 8" clearance for no vac. breaker

The reason For a Vac Breaker..

Engine Running
1) No need for it as long as the Vac Breaker seats to stop outflow of water.

Engine Just Stopping
1) Flex Vane impeller worn or water pump leaking
[Siphon break needed]

2) No Water Pump back flow issue
[Siphon break not required]

Engine not Running
1) no siphon possible

Note: Waterline of boat has no effect on Siphon breaker requirements, if your water pump is positive displacement type.[aka flex vane]

You can stop any type of Siphon by shutting off the source of flow.
--------------

The #$%^&*> seat and/or plug in the crappy little plastic valve

Mixing Elbow issue can overheat it


Jim...

 

[Rich Stidger]

FWIW, I replaced my entire vented loop a couple years ago because I couldn't find or repair the valve. $60 for the replacement. And I also have a small 3/16" hose connecting the vent to the bilge. I too have had a leaking valve make a corrosive mess on the engine.
I would make sure that replacement valves are available. I would probable even buy one as insurance against the valve becoming unavailable.

 

[smokey73]

@Rich Stidger What kind of vent valve do you have that you can install a hose to the bilge? This Scot vent valve is available for about $30. Did you use a stainless steel vented loop or a synthetic vented loop? Source if you have it?

 

[Ralph Johnstone]

Does the ABYC standard mean 8" above the fully loaded heeled waterline or the static waterline at a light load?

I believe the ABYC is suggesting an 8" clearance to avoid setting up a siphon situation in a worst case scenario. To me, nothing could be worse than defacing the side of my pretty little engine . I know, I know.

PS in trying to keep things as accurate as possible late at night, please note the correction in my flow diagram in post #8. Anyone who knows the difference between a boat and a barge knows that the exhaust gas cooling water would come from the heat exchanger.

 

[Rich Stidger]

Q.

It was a synthetic unit. IDR the brand or source. The valve had a small connection for a small hose. The valve itself used a small silicon duck bill. The brand may have been Vetus. I have had no luck buying a replacement duckbill. I'll see if I have a picture and send later.

 

[dlochner]

I believe the ABYC is suggesting an 8" clearance to avoid setting up a siphon situation in a worst case scenario. To me, nothing could be worse than defacing the side of my pretty little engine . I know, I know.

PS in trying to keep things as accurate as possible late at night, please note the correction in my flow diagram in post #8. Anyone who knows the difference between a boat and a barge knows that the exhaust gas cooling water would come from the heat exchanger.

ABYC tends to be a conservative organization when setting standards. The standards process is bit like making sausage, you really don't need to know how it is done.

Take one standard (forget the number) that an ELCI should be installed within 10 wire feet of the shore power connection. I have heard from some on the Electrical Standards committee that having an ELCI wasn't debated and the 10 foot limit was a completely arbitrary number. And watch for some major revisions in the electrical standards coming this summer.

So the 8" limit on vented loops is probably the distance a bunch of reasonable and informed people thought was a good limit.

 

[Rich Stidger]

@smokey73 . Here are the pictures that I have. Embossed on one side are the letters "ASD". Maybe this helps?

 

[JamesG161]

I believe the ABYC is suggesting an 8" clearance to avoid setting up a siphon situation in a worst case scenario

Like a back flow through a flex vane water pump, on a 15° heel?

If you have a nearly bad pump, close your sea water valve.

Jim...

 

[smokey73]

Well, I know what the source of the leak was. It looks like it is an old crack. Now I have to get the nylon (or whatever it is) piece that is still in the metal loop removed. I'm thinking of an easyout. I don't like using them to remove a metal piece from metal because if you break it, it is very hard to get it out since the easyout is hardened steel. On the nylon there is little chance of breaking the easyout.