"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?