If that's the plan, just put a big e.g. plastic garbage pail under the
outdrive and fill it up with water to protect the impeller. My opinion, the
engine thermostat won't even be opening so except for exhaust/riser cooling
water, very little water if any will actually be input to the engine cooling
system from the pail ... and the water coming out the exhaust will go back
into the pail ... 15-20 seconds, no problem. And starting up like that a
coupla times between outings, no problem ... but why bother?

"IDT 512" wrote in message
om...
"Edward Quillian" wrote in message
...
engine will overheat within about 5 minutes. Bigger problem is you will
destroy the rubber impeller on the water pump.
"IDT 512" wrote in message
om...
how long can i run the engine safely without cooling water? engine is
a
Merc 3.0L.

5 minutes??? i was thinking closer to like 15-20 seconds! I want to
start it up in the garage every once in a while and was wondering if i
can run without the flush kit to avoid getting the garage floor all
wet, otherwise id have to pull it out to the street each and every
time.

There was a thread here recently about someone loosing an impeller vane or

something like that after running a motor very briefly out of the water.

That would likely have been my problem. This was with a small outboard (4hp)
and I ran the engine very briefly out of water and it trashed the water
impeller. I got the damaged one back and I can see why it was destroyed. The
impeller has rubber vanes which make direct contact with a hard plastic
housing. Use in water works just fine as the water acts a lubricant and
removes any heat real fast. But out of water, it would be like taking a peice
of rubber and rubbing it on a peice of hard plastic. It would heat up very
fast and leave rubber on the hard plastic in no time at all. Once a little
rubber gets put down on the hard plastic, the friction goes up, more heating,
more damage..

Dont know whats in your configuration but my advice would be to not run the
engine at all out of water. Its not about overheating of the engine, its all
about the water cooling pump getting destroyed and costing you a big hassle.