Let's walk things through here, as there seems to be some confusion regarding
wet exhaust system installation, confusion caused by people looking at line
drawings from advertising brochures.

Let's take a hull with a seacock below the waterline. Just the seacock. Open
it and water flows into the hull, right? Close it and water stops. Why? The
outlet is below the waterline. Everybody agrees on that, right.

Now, let's put a length of hose on the seacock. (We called it a "hose", but
that "hose" could be the entire engine raw water cooling system. Still, we
will call it "hose".) Now, open the seacock and what happens. If the hose
outlet is below the waterline, water flows into the hull. Of course, everybody
says, the outlet is below the water line. Now, make the hose stop right at the
waterline, water stops at the top but doesn't flow into the hull (unless the
boat rocks or heels). Now, make the hose (remember, "hose" can mean the entire
engine raw water cooling system) **at least** six inches above the water line.
No water flows into the hull (of course) while the boat is level and there is
little chance water will flow into the hull under most happenstances of rocking
or heeling. Great.

Now, let's take that "hose" that opens **at least** six inches above the water
line and turn on its pump (i.e. start the engine and running its raw water
pump). What happens? Of course the engine pumps water out the top of the hose
and water flows into the hull. This water must be removed from the hull (or in
this case, the wet exhaust system), and is removed by the pressure of the
burned exhaust gases from the engine. Hence, a "wet exhaust". Notice that
when the engine stops running the water stops flowing because the outlet of the
hose is above the waterline.

"But wait a minute," somebody says, "what happens if we place a u-shaped end on
the hose and put an anti-siphon valve in it?".

Same, same **as along** the outlet of the hose is above the water line. The
engine stops the water flow stops because the outlet is higher than the water
line, the anti-siphon adds nothing but expense.

This time lets make the end of the u-shape below the water line (dumb, dumb,
dumb but let's address that in a minute). *IF* the top of the u-shape is below
the waterline the whole thing acts as if the hose were straight up. In other
words the entire hose is below the water line and if the seacock is open water
flows into the hull and/or exhaust system. Note that any anti-siphon valve
installed anywhere in this system is useless, for there is no siphon just a
hose that starts below the water line, always stays below the water line and
ends below the water line. Open the seacock water flows in and MUST be pumped
out by the running engine. This is a forbidden installation. Dumb, dumb,
dumb.

Now, let's make the **top** of the u-shape above the waterline but the outlet
below. What happens when you open the seacock? Not much, the water flows into
the hose and up until it equalizes and then stops flowing. But, turn on the
engine to a pump water and fill the entire hose with water -- from the seacock
to the top of the u-shape and down to the outlet which is below the water line
and open to the inside of the hull and/or exhaust system. Water flows and must
be pumped out (by engine exhaust pressure).

Here comes the potential for trouble.

First, when the pump stops there is in fact a siphoning effect (because while
the top of the u-shape is above the water line, the outlet is below). Under
these conditions (should the exhaust installer fail in his job, AND the boat
designer put the engine very low in the boat) there is a need to "break siphon"
by installing an anti-siphon valve. Note that this **requires** the
anti-siphon valve to be above the waterline under all potential boat heeling
positions.

Second, anti-siphon valves fail due to crud in the water. They always do
eventually. The solution for this is regular preventive maintenance. (There
is another solution to avoid anti-siphon crudding up but I have never seen it
but once.)

In other words, an engine with its water injection point of its wet exhaust
below the water line is in danger of at some point filling the exhaust system
with salt water with the engine shut off. A competent surveyor would fail a
boat with such an installation. If there was no way in hell the water
injection point could be moved higher (due to stupidity or deliberate choice by
the boat designer) then the insurance company could decline coverage or
increase its premiums to cover the greater potential for boat loss. Sooner or
later the wet exhaust is going to flood unless the boat owner is deligent about
keeping the anti-siphon clean AND is damned lucky nothing flukey happens
between maintenance events.

The solution is to mount the water injection outlet **at least** six inches
above any potential water line.

It is in the installation instruction that come with a water injection elbow.
RTFM, guys. RTFM

"JAXAshby" wrote in message
...

snip nonsense where jaxie tries to look intelligent, but fails


Here comes the potential for trouble.

First, when the pump stops there is in fact a siphoning effect (because while
the top of the u-shape is above the water line, the outlet is below). Under
these conditions (should the exhaust installer fail in his job, AND the boat
designer put the engine very low in the boat) there is a need to "break
siphon"
by installing an anti-siphon valve. Note that this **requires** the
anti-siphon valve to be above the waterline under all potential boat heeling
positions.

I have stated many times that all heel angles and loading condition must be
considred. You keep claiming that engines are not installed bleow the
waterline, but this is clearly not the case. The engine is below the waterline
on almost all sailboats. You should check them out sometime.



Second, anti-siphon valves fail due to crud in the water. They always do
eventually. The solution for this is regular preventive maintenance.

Yes, this is a problem - boats require maintenance. However, this is not too
much of a problem with a modern setup. The siphon break can simply be a vent
hole with a tube that drains overboard, or into a cockpit drain. As long as
water flows out the tube, the siphon break is not clogged. On my boat, the
siphon break flow is visible from the helm and is a good way to tell that all is
well. Here's the installation manual for the Vetus:

http://www.vetus.nl/pdf/03M0405_0499.htm

(There
is another solution to avoid anti-siphon crudding up but I have never seen it
but once.)

Not surprising that you've never seen it and don't want to tell us about it.



In other words, an engine with its water injection point of its wet exhaust
below the water line

You mean the majority of sailboats.

is in danger of at some point filling the exhaust system
with salt water with the engine shut off. A competent surveyor would fail a
boat with such an installation.

Nonsense. In fact, the 41 foot center cockpit I mentioned was exhaustively
surveyed by a gentleman considered the best surveyor of older boats on the East
Coast. (I won't mention his name because jaxie would just use it as an excuse
to demean his good name.) Actually, any surveyor would fail a boat that
doesn't have a siphon break when its needed.

If there was no way in hell the water
injection point could be moved higher (due to stupidity or deliberate choice
by
the boat designer) then the insurance company could decline coverage or
increase its premiums to cover the greater potential for boat loss.

So why is it that the ABYC never mentions this problem? They clearly recognize
the issue, since they require a a siphon break in this situation. The are a
number of other areas where they say "This should be avoided ..." but they don't
in this case.


Sooner or
later the wet exhaust is going to flood unless the boat owner is deligent
about
keeping the anti-siphon clean

Or installs a proper vent, like the Vetus.

AND is damned lucky nothing flukey happens
between maintenance events.

Like being run down by you?


The solution is to mount the water injection outlet **at least** six inches
above any potential water line.

That would work, but unfortunately most sailboats are designed so that it is not
possible. Remember, the ABYC stardard says the issue exists if the exhaust
manifold, not just the injection point, is below the water line. Since the
manifold is about 8 inches from the prop shaft, its pretty hard to satisfy this
without having an extreme down angle and an 8 foot shaft!


It is in the installation instruction that come with a water injection elbow.
RTFM, guys. RTFM

What manual is that, jaxie? Not the Yanmar installation guide - I posted that
and it says to use an siphon break. Not the ABYC guidelines - I posted that and
it says to use an siphon break. Do you have a secret manual you'd like to share
with us?

wrote:

[snip all but the important stuff]


PLEASE!!!! don't anyone follow jeffies ramblings. you can get hurt, and
jeffies doesn't care a wit.

What's your claim jaxie, that people are going to remount their engine based on
my advice? All I've done is to quote the ABYC standards - your the one claiming
that all the advice of the experts is faulty! Do you actually thing that
another would be so stupid as to believe you??? Do you really think you have
any slight thread of credibility????? Just how delusional are you jaxie?



"JAXAshby" wrote in message
...
wrote:

[snip all but the important stuff]


PLEASE!!!! don't anyone follow jeffies ramblings. you can get hurt, and
jeffies doesn't care a wit.

What's your claim jaxie, that people are going to remount their engine based
on
my advice?

no, but there is a chance someone just as dumb as you will mount a water
injection unit below the water line, a forbidden practise even if it took you
several days to even begin to understand why.

I write an explanation of something utterly simple, and write it in words even
a 11 year old girl would understand, and jeffies dismisses it as an attempt "to
look intelligent" thusly:

snip nonsense where jaxie tries to look intelligent, but fails


my, my, my. jeffies considers the use of words understandable by a sixth grade
girl to be putting on intellectual airs. I wonder what jeffies would think of
the New York Times (should he ever see one), for they write so eighth grade
girls can understand.

"JAXAshby" wrote in message
...
What's your claim jaxie, that people are going to remount their engine based
on
my advice?

no, but there is a chance someone just as dumb as you will mount a water
injection unit below the water line, a forbidden practise even if it took you
several days to even begin to understand why.

If the engine is below the waterline, its impossible to have the exhaust
manifold above the waterline. Unless, of course, you have a "magic manifold"
that can be mounted several feet away from the engine.

You can use a special elbow to raise the injection point a few inches, but that
does not satisfy the requirement that a siphon break is required if the manifold
is below the waterline. Do you know what a manifold is, jaxie? Can you
explain how you're going to raise that up?

Even if you raise the injection point a few inches, on many boats that will not
raise it above the waterline at all angles of heel and at all loading.

Squirm all you want, jaxie, you haven't explained how you can have the shaft
several feet below the waterline while the engine is above. Are you saying the
shaft should be 20 feet long?

If the engine is below the waterline, its impossible to have the exhaust
manifold above the waterline.

really? see below

Unless, of course, you have a "magic manifold"
that can be mounted several feet away from the engine.

You can use a special elbow to raise the injection point a few inches

"a few inches"?? at least six inches above the water line. and there is not a
think "special" about it. the pipe is solid bolted to the manifold, an elbow
turns the pipe **UP**, jeffies, until high enough, then the water injection
elbow is mounted, etc.

what word don't you understand?

but that
does not satisfy the requirement that a siphon break is required if the
manifold
is below the waterline.

jeffies, it is NOT the manifold you need to worry about (anymore than you need
to worry about where the oil pump is) BUT where the water (from outside the
hull) empties into the system, THEREFORE if the water injection point is above
the water line **there is no siphon potential**. None.

jeffies, this is easy stuff. as in E Z.

kriste almighty, jeffies, I explained it to you in words understandable by an
11 year old girl. wake up, dude. Get your wife to explain it to you this
time.

"JAXAshby" wrote in message
...
If the engine is below the waterline, its impossible to have the exhaust
manifold above the waterline.

really? see below

Yes really, its the standard, and its the law. The ABYC says a siphon break is
"recommended in applications where the exhaust manifold may be below the
waterline at any angle of heel." And the Code of Federal Regulations, 46CFR182
says that the ABYC standard is the law in this area. The CFR also says the
injection must be as close as possible to the manifold.

So while you can claim that the injection point is the important point to
measure, the law says otherwise. Failure to abide by this would certainly mean
failing a survey, and making it impossible to insure the boat.




Unless, of course, you have a "magic manifold"
that can be mounted several feet away from the engine.

You can use a special elbow to raise the injection point a few inches

"a few inches"?? at least six inches above the water line.

Actually its just 5 inches higher. When the boat is "at repose." Let it heel
45 degrees, and its only 3.5 inches higher.

and there is not a
think "special" about it. the pipe is solid bolted to the manifold, an elbow
turns the pipe **UP**, jeffies, until high enough, then the water injection
elbow is mounted, etc.

It's special in the sense that in the Yanmar parts catalog the "straight pipe"
is the standard one, while the raised elbow is listed as "optional equipment."
Admittedly, almost all sailboats would use the raised elbow. (A friend has a
new YM engine with the straight pipe, but its a catamaran with a single engine
perched a foot above the water driving a Sonic Leg.)



what word don't you understand?

I understand perfectly. Why is it that you continually claim the standard and
the law should be ignored? Its very simple: if the manifold is below the
waterline, a siphon break should be installed. Failure to do so means failing
the survey, no insurance, no marina, no sale.


but that
does not satisfy the requirement that a siphon break is required if the
manifold
is below the waterline.

jeffies, it is NOT the manifold you need to worry about (anymore than you need
to worry about where the oil pump is) BUT where the water (from outside the
hull) empties into the system, THEREFORE if the water injection point is above
the water line **there is no siphon potential**. None.

That's not what the standard says. That's not what the law says. Why are you
claiming the law should be ignored?


jeffies, this is easy stuff. as in E Z.

It sure is, jaxie, and you still don't get it.

You still haven't explained how the engine can be mounted so that the manifold
(or even the injection point) can stay above the waterline. In any center
cockpit boat, for example. the entire engine will be well below the waterline,
even before heeling is considered. Raising the injection point 5 inches still
won't help.