That one has been in my urban legend category for a while.

The muffs start leaking when you turn the water on full so I really don't
see how you can get enough pressure to damage anything. Also you've seen
that impeller, it is pretty tough. I've always had a hard time seeing how
any water pressure could do anything to it. It may be possible to blow out
some of the gaskets under the pump housing with enough pressure but I still
don't see how you can get the muffs to stay on enough to build up that
pressure.

"Boots Crofoot" wrote in message
. ..
One more think on using the muffs. DO NOT run the hose at
full blast. Just crack a little cause too much water
pressure and flow will damage the rubber water pump
impellers. Take it from an x merc. mech.
"Lawrence James" wrote in
message
ink.net...
Flushing with the muffs will flush the entire coling system
including the
outdrive. The raw water pump is in the outdrive. Run for
about 5 minutes
or until the temp gauge shows normal operating temp to
insure that the
thermostat opens. You really can't beat this flushing
technique, it is
cheap and thorough.

A closed cooling system can increase the life of some of
your engine
components. Unfortunately the parts that will deteriorate
the fastest in
salt water are the exhaust manifolds and exhaust risers.
The combination of
hot exhaust and salt water makes an extra corrosive mix. No
closed cooling
system will include the exhaust risers. The raw water from
the closed
system heat exchanger is used to cool the risers and then
dumps into the
exhaust. Some closed systems will include the exhaust
manifolds and some
will not. It takes more cooling capacity to include the
exhaust manifolds.
There are different gaskets and hose connections for the
exhaust system when
you convert them to a closed system.

In salt water depending on amount of use the life of exhaust
risers can be
as little as 3 to 5 years. Manifolds a few years longer.
They should be
removed and inspected when they start to reach these ages.
The engine cast
iron block its self will wear out long before the effects of
corrosion will
matter. There are lots of raw water cooled inboard blocks
running around
and sitting in salt water for 20 years or longer.

"Rich" wrote in message
. com...
I'm fairly new to motor boats, we now have a Mercruiser
5.0, operated in
sal****er only. Is there a better way to flush other than
the "ears" over
the outdrive? I thought at one time there was some kind
of setup to flush
the motor without running it, anyone know for sure?

TIA
Rich