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Old 28-07-2021, 19:52   #1
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Throughly BRILLIANT idea for exhaust improvement

Yeah right!

Reading another thread and having had a recent “issue” I came up with an idea.

PROBLEM:
Exhaust elbow is below water line. Past attempts to raise the elbow have not been successful and have resulted in potentially serious failures.

The current solution is to use an HDI aftermarket elbow (very good quality and cost) but there is the potential of engine flooding should the anti-siphon fail. In fact the Owner (me) made a dumb s^*t move and flooded the engine. I have recovered without further problems but am now sensitive (hyper?) to the risk.

TRADITIONAL SOLUTION:
Raise the elbow above waterline so that the sill the water must pass over is above the water line. This means raising the entire elbow, which is proving to not feasible. The unsupported weight of the elbow is causing various failures.

POTENTIAL SOLUTION:
The elbow has a fitting the sea water inlet fits to. Add a length of hose to the sea water line so that there is a loop in the line which extends above the water line. This will provide a abive water line sill making a siphon impossible.

There is the possibility that if the water line is completely filled with water the sill would not work. Therefore it MAY be necessary to insert some kind of can in the line at the apex of the loop, where the sill would be.

The sill, being above water line defeats a siphon. And because it has flexible hose connected to it its weight could be supported from above, and thus not mechanically stress the elbow connections or body.

Wada you guys think? Possible?
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Old 28-07-2021, 19:59   #2
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Re: Throughly BRILLIANT idea for exhaust improvement

like this?
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Old 28-07-2021, 20:06   #3
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Re: Throughly BRILLIANT idea for exhaust improvement

Never mind, brain fart.

I am just reinventing a traditional anti-siphon.
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Old 28-07-2021, 21:49   #4
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Re: Throughly BRILLIANT idea for exhaust improvement

Quote:
Originally Posted by hpeer View Post
Never mind, brain fart.

I am just reinventing a traditional anti-siphon.
And there was I getting excited when I read the thread title; ah well, never mind!

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Old 29-07-2021, 05:17   #5
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Re: Throughly BRILLIANT idea for exhaust improvement

Reefmagnate,

Sort of. Do you have a link to where that image came from?

I BELIEVE that is showing a RAW water cooled set up because it is not showing the cooling water being injected into the elbow.

The “problem” I am trying to fix is only if the vented loop fails for some reason.

This all comes about because I did something stupid, now I an second guessing myself.

Just to be clear there are 2 anti siphon devices in that drawing. One around the elbow and the goose neck. Because there are 2 sources; the exhaust and the through hull.
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Old 29-07-2021, 05:49   #6
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Re: Throughly BRILLIANT idea for exhaust improvement

Some technical info:
http://realitycheck.me/docs/waterliftmuffler.pdf
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Old 29-07-2021, 05:51   #7
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Re: Throughly BRILLIANT idea for exhaust improvement

Quote:
Originally Posted by hpeer View Post
Reefmagnate,

Sort of. Do you have a link to where that image came from?

I BELIEVE that is showing a RAW water cooled set up because it is not showing the cooling water being injected into the elbow.

The “problem” I am trying to fix is only if the vented loop fails for some reason.

This all comes about because I did something stupid, now I an second guessing myself.

Just to be clear there are 2 anti siphon devices in that drawing. One around the elbow and the goose neck. Because there are 2 sources; the exhaust and the through hull.


That’s showing a raw or fresh cooled engine. The one in the exhaust is mislabeled as an anti siphon loop, it doesn’t have a siphon break on it at all. The water into the elbow is clearly depicted in the image.

You’re spinning your wheels here.
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Old 29-07-2021, 06:07   #8
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Re: Throughly BRILLIANT idea for exhaust improvement

Quote:
Originally Posted by hpeer View Post
Reefmagnate,

Sort of. Do you have a link to where that image came from?

I BELIEVE that is showing a RAW water cooled set up because it is not showing the cooling water being injected into the elbow.

The “problem” I am trying to fix is only if the vented loop fails for some reason.

This all comes about because I did something stupid, now I an second guessing myself.

Just to be clear there are 2 anti siphon devices in that drawing. One around the elbow and the goose neck. Because there are 2 sources; the exhaust and the through hull.

Easiest way to solve the vented loop failure issue is to replace the problematic joker valve with a "pisser" tube that drains into, say, a cockpit drain. Done this way it can be used to give the same visual indication that water is flowing in the raw cooling circuit as an outboard's does. The tube only needs to be small in diameter.



The "anti syphon loop" bit is just raised enough above the waterline to prevent water ingress. I don't think that they have joker valves fitted for the most part due to the risk of exhaust fumes filling an enclosed area.
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Old 29-07-2021, 07:50   #9
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Re: Throughly BRILLIANT idea for exhaust improvement

Yeah, I am obsessing.

Enough.

Thanks.
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Old 29-07-2021, 07:53   #10
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Re: Throughly BRILLIANT idea for exhaust improvement

Quote:
Originally Posted by Reefmagnet View Post
Easiest way to solve the vented loop failure issue is to replace the problematic joker valve with a "pisser" tube that drains into, say, a cockpit drain. Done this way it can be used to give the same visual indication that water is flowing in the raw cooling circuit as an outboard's does. The tube only needs to be small in diameter.



The "anti syphon loop" bit is just raised enough above the waterline to prevent water ingress. I don't think that they have joker valves fitted for the most part due to the risk of exhaust fumes filling an enclosed area.

I can't think of any good reason to install any anti-siphon valve when you can create a system without any moving parts and get a visual indicator that the system is properly functioning.
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Old 29-07-2021, 14:45   #11
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Re: Throughly BRILLIANT idea for exhaust improvement

Put in a dry exhaust and keel coolers. Solves an awful lot of problems. No salt water coming into the boat (at least for this application), no chance of sucking up sand, plugging the strainer, and overheating the engine during a grounding, no salt water pump on the engine, no heat exchanger, no salt water into the exhaust system.
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Old 29-07-2021, 16:36   #12
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Re: Throughly BRILLIANT idea for exhaust improvement

Scorpius,

I have thought about it for just those reasons.
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Old 29-07-2021, 18:11   #13
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Throughly BRILLIANT idea for exhaust improvement

FYI my engine has a ‘dry stack’ (iron pipe off the exhaust manifold) to raise the height of the mixing elbow, and yes, it’s unsupported weight was causing various cracks and catastrophic failures my first year with the boat.

I used a length of angle iron and a couple heavy duty u bolts to attach the top of the dry stack down (and fwd) to the engine. This fix has lasted for about 8 years now. It prevents the heavy exhaust elbow from moving fore and aft relative to the engine.
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Old 30-07-2021, 09:46   #14
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Re: Throughly BRILLIANT idea for exhaust improvement

Chris,

I had looked at the same kind of fix but could not find any real good candidates. I had a mechanic who also suggested that fix and he also could not come up with a suitable attachment.

Anyway, it is done now.

I do dislike the common marine exhaust solution. Keel coolers also have some disadvantages and they look a bit vulnerable.
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Old 30-07-2021, 10:58   #15
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Re: Throughly BRILLIANT idea for exhaust improvement

Glad you are all set.

FYI some of the posts here seem to suggest that simply routing the piping above the waterline is enough to break a siphon. It is not! The magic (and danger!) of a siphon is that it can lift the water higher than the water level as long as the exit point is below the water line.

Take a length of hose and drop one end of it overboard just below the water's surface, loop the hose over your boom, and finally down into your bilge. That loop around your boom is far above the water line, right? Yet, if that hose is allowed to fill with water a siphon will develop that will flood your bilge.

A siphon break is more than just a loop above the water line, its a loop above the waterline with an air vent (often a check valve) to break the siphon if a vaccum develops.
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