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Old 10-22-2016, 05:34 PM   #1
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Question Engine exhaust vacuum break

I found a few ounces of water in my engine room today. Looking for a reason, I notice two of my ceiling panels in the engine room have wet edges. The panels are finished wood so the wet edges show some warpage.

When I take the panels down, there is signs of water and salt. I am thinking my problem is coming from a vented loop / vacuum breaker that is mounted above the ceiling panel.

The siphon break / vacuum breaker is a Scot Pump 3/8" - a plastic basket with spring/ball inside. Are there better products to use for this? I am considering building a box for around the vented loop so it cannot put water into the space above the ceiling panel.

http://www.boatswainslocker.com/cont...pages/VB38.pdf
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Old 10-22-2016, 05:55 PM   #2
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Mine is an expensive "T" in the line with a pinhole in it to allow ware and air to be exchanged via small tubing to a tiny thru hull well above the waterline.

Check Vetus engine exhaust anti siphon valves.

You can make your own for a lot cheaper if you can find the right bronze parts locally.
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Old 10-22-2016, 06:01 PM   #3
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Henry,
You can get a siphon break which is designed with a small vent hose is run to a skin fitting above the waterline. I know Vetus make a few versions.
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Old 10-22-2016, 06:12 PM   #4
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I will bet that your vacuum breaker is weeping and letting raw water leak down to the panels below. This happened to me on a sail boat and it corroded the thin engine oil distribution tubing.


Forespar and maybe others have an optional check valve that works with their vented loops and has a hose barb that you can attach a hose and route it down to the bilge. See Defender.com Search Results: forespar anti syphon


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Old 10-22-2016, 07:10 PM   #5
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The only way to be sure the system works and doesnt leak inside the boat is to run the anti siphon air tube to the outside of the boat. See the figures.

A in the first diagram us what I used and the second picture is the devicd.

Once I understood it is just an expensive "T" to an overboard thruhull, I know it could be had for a lot less money if you have access to fittings without the expensive shipping....or a cheaper piece with just a hose barb instead of the anti siphon valve.

At idle, no water comes out the thruhull...above say 1000 RPM, and the flow steadily increases with RPM.
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Old 10-22-2016, 10:51 PM   #6
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I have reviewed the installation sheet on the Vetus product. My engine room does not have enough headroom to install the loop 16" above the waterline. Tomorrow, I am going to measure and mark my waterline inside the engine room to see what my options might be.

Thank you
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Old 10-23-2016, 07:59 AM   #7
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Quote:
Originally Posted by HenryD View Post
I have reviewed the installation sheet on the Vetus product. My engine room does not have enough headroom to install the loop 16" above the waterline. Tomorrow, I am going to measure and mark my waterline inside the engine room to see what my options might be.

Thank you
Don't worry about the 16" at the outlet, as long as it runs downhill I think you will be fine....just as long as it isn't submerged so it can drain and allow air back up.

Plus you could run that line the full length of your boat if need be, so up into a locker would be fine.

The higher you run it, the less water will come out of it and as long as it will drain back to allow air into the elbow to break a siphon...all is good. It just can't have too much residual water to drain back and fill your exhaust into your exhaust manifold....but that should be easy to see or calculate.
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