Ok here's a direct quite. Read it slowly. Take your time.

"Problems occur because on almost all sailboats, and on many powerboats,
the engine is installed below the waterline. Even if it's not below the
waterline when the boat is at rest, the engine may well end up there
when the boat heels, or when it is heavily loaded. This latter case can
be particularly dangerous: because the boat's designer or engine
installer may not have adequately planned for it. If the engine is or
any time below the waterline, any cooling circuit that allows raw water
into the exhaust has the potential to set up a siphon action. Water may
siphon in from the water injection side; or, if the exhaust outlet is
below the waterline, from the exhaust outlet side."

See the last two words???

Cheers

JAXAshby wrote:

nave, go look at a wet exhaust, any wet exhaust. you simply don't understand
what such is.


Dud? Let me explain at a level a child should understand. You run the
engine -it gets hot. You turn it off. You raise the sails so the boat
heels and puts the exhaust under water. The engine cools and water gets
sucked in 'cos the siphon break valve no longer works...

get it?

Cheers

JAXAshby wrote:

Now tell us why you think you don't need an antisiphon valve. Vague
references to gas laws are required.


you can't siphon water uphill using the weight of exhaust gas going

downhill.

dud!