I guess, if you haven't already, find out what the recommended pressure is.
I located my info for Mercurys (with a "Mercury" gauge). The lowest is
"6-12psi" for 50/60/65/70 3 cyl and the highest is "15-25psi" for a lot of
engines, most all the V-6's and all #'s are at "above 5000rpm".
I'm with you---2-4 psi isn't enough. A phone call to any dealer service
dept should get you the specs. My bet is either a leak or restriction
between the pump and the block. 'Course, it could also be a blockage before
the pump. It's easy enough to change the foot which, like you said, would
confirm or eliminate "half" the potential problems.
Good luck.
LD

"Greg" wrote in message
...
I have the guage in the bottom of the water manifold where they feed to
the
fuel coolers and eventually out the pee hole.
Thelflex suggests that as one of the points. This is all with the boat in
the
water running. It will not fail on a trailer. The boat needs to be pushing
water to be running hard enough to overheat.
With the thermostat out it acts similar at speed, overhreating around
4000, but
up to about 2000 RPM this thing won't even get hot enough to make the
computer
happy (100-110 degrees, without the thermostat). It runs like a car in
"limp
home mode".
I only tried that once, just to see if there reallty was TWO bad
thermostats.
(I am on #3 now in the $300 hunt).
I really think this is just not pumping enough water and under a load it
overloads the ability to cool. Simple huh?
You can see why I really want to swap the whole damned foot.