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Old 29-05-2020, 09:58   #1
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Vacuum breaker on cooling system

I just installed a new Yanmar 4JH5E in my 1990 Hunter 45. All the electronics leave me thinking that for sure they are going to fail. There is a 5 year warranty IF you follow all sorts of inspection protocols. The dealer wants to see a vacuum breaker on the cooling system but has no idea where to install. Any ideas? I know it has to be on the discharge side of the water pump">raw water pump, but how?
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Old 29-05-2020, 10:32   #2
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Re: Vacuum breaker on cooling system

Unless Yanmar says differently, you can put the anti-siphon pretty much anywhere it is convenient as long as it is before the exhaust mixing elbow. On my (Volvo) it is immediately after the raw water pump.

In my case, I do not have a check valve style a-siphon, just an 1/8 inch orifice led to a drain line overboard that I can easily see. This avoids the salt plug that occasionally occurs with valve-type a-siphons and is an easy tell-tale that all is well on the raw water side.
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Old 29-05-2020, 17:21   #3
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Re: Vacuum breaker on cooling system

Thank you
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Old 29-05-2020, 17:55   #4
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Re: Vacuum breaker on cooling system

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Originally Posted by Wolverine View Post
Thank you


Is the new Yanmar replacing an older model Yanmar?
The vent loop ( siphon break ) is critical to the survival of your new engine, use good quality hose, avoid automatic anti siphon valves unless you’re prepared to verify their operation at regular intervals and most of all , have a good understanding of why the vent loop is there and how it actually works.
Installing a new engine is a great opportunity to review and repair/upgrade the stuff that keeps your engine running.... the raw water intake system, the fuel supply, the shaft seal and coupling, the exhaust system and maybe the control cables.
Pete.
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Old 29-05-2020, 18:10   #5
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Re: Vacuum breaker on cooling system

Pete, The problem is that I am pretty sure you are supposed to install an anti syphon valve on the raw water system just before the water reaches the exhaust elbow but there is no place to physically attach an automatic valve. has anyone succeeded in communicating with Yanmar directly? Since they sold the engine and they have the requirement you would think they have made provision.
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Old 29-05-2020, 18:34   #6
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Re: Vacuum breaker on cooling system

Surely there is a hose from something that supplies the raw water to the heat exchanger? Often it’s a very short hose that you remove and Replace with a loop of hose that has the siphon break in the middle. My original hose was about three inches long, that is where I put my siphon break, just trivia but my boat was 30 yrs old before she got a siphon break, if the motor is above water line, they may not need one, but it’s good Insurence for when your heeled over sailing.

Now on my boat there are a couple of tubes that have short hoses on each end, these tubes are easily removed and are not critical, they just carry water, for instance I removed one right after the raw water pump and installed all hose to the oil cooler, that way I could mount a strainer to catch broken bits of raw water impeller if it breaks up again.

Mine is a Groco bronze siphon break and does have the rubber valve, but in truth the way Jamass has done it is better because it doesn’t have a valve that can stick, and if you run the little tube that water will run out so that it’s visible, then you have a way of seeing you have cooling water, exactly like an outboard.

In this picture you can see Where the short hose connected the heat exchanger to the Exhaust elbow. I removed it and installed the orange hose, the black hose directly underneath takes the water from the oil cooler to the heat exchanger, it could also be removed and longer hose loop installed for a vacuum break.
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Old 29-05-2020, 19:17   #7
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Re: Vacuum breaker on cooling system

Thanks for the tip. It just occurred to me that there is a pipe plug right on the side of the exhaust elbow. Maybe I could go straight from there up to an anti - syphon valve well above the water line.
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Old 29-05-2020, 19:23   #8
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Vacuum breaker on cooling system

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Originally Posted by Wolverine View Post
Thanks for the tip. It just occurred to me that there is a pipe plug right on the side of the exhaust elbow. Maybe I could go straight from there up to an anti - syphon valve well above the water line.


It’s not going to do any good unless the antisiphon valve is inline with the flow of raw water in the cooling circuit.

Post a photo of your mixing elbow and someone can point out where to put the valve.
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Old 29-05-2020, 19:45   #9
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Re: Vacuum breaker on cooling system

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It’s not going to do any good unless the antisiphon valve is inline with the flow of raw water in the cooling circuit.

Post a photo of your mixing elbow and someone can point out where to put the valve.
I have never seen one installed like he say’s but it ought to work? Have to find a siphon break that isn’t meant to be inline of course.
I agree with a picture though, I’m sure there is a way to install a normal siphon break.
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Old 29-05-2020, 19:55   #10
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Re: Vacuum breaker on cooling system

i am off the boat for a few days. I will take pictures and post hoping one of us can figure it out. So far, a 64 Pilot's picture is a help. Back at you in a few days.
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Old 29-05-2020, 20:11   #11
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Re: Vacuum breaker on cooling system

Oh, my.... No, no, and no!

The anti-siphon can not go “anywhere.”

Putting it below the water line of the boat does absolutely NOTHING to protect the engine from back flooding and in fact can sink the boat. If, like most sailboats, the exhaust elbow of your engine is below, or close to the water line this is a CRITICAL part, and you need to understand where it goes and why.

If you do not understand, and won’t, can’t or just haven’t done the research, you need to hire someone who has.

Water flows from the raw water pump, into the engine heat exchanger, then into the exhaust elbow. The anti-syphon MUST go between the heat exchanger and the elbow. From the heat exchanger, the water must flow UP a hose AT LEAST 16 inches above the water line at all angles of heel, then back down to the exhaust elbow. The siphon break must go at the very top of this hose. Nowhere else is correct.

The siphon break can be a small diameter hose taken off to a drain, or a proprietary check valve. If using a hose, many people route it to the cockpit just above a drain so water flow is obvious at the helm.

If you don’t know how and where to install a siphon break it is very unlikely that you will get the rest of the exhaust system right. All you have to do is search this forum for “flooded engine” to know that there are LOT of poorly designed exhaust systems out there, and a lot of engines have died because of it. Including new engines. Lengths, heights, diameters, volumes, are all critical.

It is very unlikely that Yanmar would warrantee damage caused by seawater flooding, since that is always caused by bad installations or maintenance, and that is out of their control.
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Old 29-05-2020, 20:14   #12
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Re: Vacuum breaker on cooling system

Yanmar's repowering manual (presumably what the dealer is quoting) says:

Quote:
Cooling Water For The Engine, Not In The Engine
The engine’s raw water intake must be equipped with a proper seacock followed by a raw water strainer, preferably one that can be opened easily, without tools, and which will reseal without the need for a new gasket. Be certain that the new engine installation design takes account of the height of the engine relative to the waterline. Engine installations that place the exhaust elbow near or below the waterline, must include a vacuum breaker / antisiphon valve in the raw water discharge line, at a point prior to injection of cooling water into a water cooled exhaust system. This valve must be located where it can be readily checked and cleaned.
What they neglect to say is this pretty much means taking off one of the factory supplied hoses, either between the raw water pump and the HX or between the HX and the exhaust elbow and replacing it with a longer length (at your expense) that loops up well above the waterline and has an anti-siphon device of some kind.

For our boat we do, as suggested above, just have a 1/8"/3mm hose that comes out of a tee at a high point and exits the boat very near the sheer. This provides a telltale much like those on outboards to show raw water flow. You do want this small, you are diverting some water from the exhaust system.
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Old 29-05-2020, 20:17   #13
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Re: Vacuum breaker on cooling system

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Originally Posted by Wolverine View Post
Pete, The problem is that I am pretty sure you are supposed to install an anti syphon valve on the raw water system just before the water reaches the exhaust elbow but there is no place to physically attach an automatic valve. has anyone succeeded in communicating with Yanmar directly? Since they sold the engine and they have the requirement you would think they have made provision.
Hi, on mine the syphon break is fitted in the hose between the exit from the heat exchanger and the injection point on the exhaust elbow. The hose is approx 1.5 m long running up above the water line to the vented loop and back down to the elbow. There is no valve as such, just a small dia hose from the loop to a cockpit drain. Easy to see if there is water flowing.
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Old 29-05-2020, 20:21   #14
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Re: Vacuum breaker on cooling system

I can't believe the number of well thought out replies I have received! Thanks everyone.
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Old 30-05-2020, 17:55   #15
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Re: Vacuum breaker on cooling system

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I can't believe the number of well thought out replies I have received! Thanks everyone.


Wise words indeed from A64pilot and a good photo showing how damned hard it can be to get the loop hoses in the correct place on some engines.
Pete Jarrett
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