89 200 cooling issue

[BQUICK]

Has weaker than normal pee stream....no overheating...recent impeller.
I notice that when I shut it off it does not continue to pee for a while like my others. Telltale clear of debris. Thought poppit not sealing and water draining it new made no difference.

I hear a slight hissing and the telltale after shut off. I suspect exhaust plate leak but no water on any plugs.