Along with everyone else, I agree that:
1. You have an idiot for a mechanic
2. You need an impeller.
AND-
3. You should kick that moron "mechanic's" ass for almost roasting your
engine with his stupidity.

"Bobo" wrote in message
.com...
I recently bought a 1990 Searay 180 Bowrider I/O V-6 (4.3 L) Mercrusier. I
have noticed that the baot always runs cool (140-145) when I am at a
decent
speed. When I slow down to 3-5 mph, or when I start up after being shut
down
for a few minutes, the temp goes to about 220. Once I get up to speed, it
goes back down to 145 again. Also after I have shut down, on trying to
start
the boat I get the alarm and the temp is pegged. My mechanic says not to
worry. Any Ideas?