Here's what I found out the hard way today: In the fresh-water cooled engine where the reserve tank on the heat exchanger is higher than the thermostat, removing the stat will allow gobs of AF to spill out until the levels are even -- essentially, most of the contents of the heat exchanger reserve tank. Sooooo....siphon the AF out of the tank first, then it's safe to unbolt the stat. And when you have replace it and rebolted the assembly, you can put the AF back into the tank.
Joel Albert, Potomac MD
"Charlie B" - 1988 32' FBS
Twin 318's/FWC/16x15 nibral props
docked Deale, MD