If it's anything like a merc the housing is two pieces.

"Jim" wrote in message
om...
I took my '88 4.3L out for a cruise today before storing it and had
overheating problems. So I brought it home and hooked it up to the
flusher. If I pull the inlet hose on the thermostat housing there is
water when it's running. So I pulled the thermostat housing expecting
to find a thermostat in the intake manifold, but there isn't one
there. Rather there seems to be one built into the housing that can't
be changed? I must be missing something, right?