Kevin,

You didn't say if the boat was in or out of water. If out of water the
best procedure IMO is to start the engine on the hose w/earmuffs on and
run it up to temp so t-stat opens. Dump in fuel stabilizer previously
so it circulates through the fuel system into the carb/throttle body.

Once at op temperature shut off engine and water & pull all drains. My
1999 5.7 Merc has 5 - two on the block, two on the manifolds, and one
on the low point of the fat circ pump hose. Then stick a funnel in a
short section of hose to the earmuffs and ready 3 gallons of marine/RV
antifreeze. Have helper start pouring antifreeze into funnel and start
the engine. By the time 2 gallons have been poured the cooling system
should be pretty much full and by the 3rd gallon red antifreeze will by
****ing out the exhaust.

At this point blast the fogging spray into the carb throat (remove
spark arrestor) until the engine dies. Some like to use Mystery Oil for
this. At this point the antifreeze has displaced any residual water in
the block and the fogging spray has protected the cylinders from
corrosion.

This method was shown to me by a marine tech and has worked quite well
for the six seasons we've had our boat. There are other ways to
accomplish the same thing, but the important thing is to get any water
out of the block to prevent freezing damage and protect the combustion
chambers from corrosion.

Wooly