1996 Evinrude Intruder 150hp Water Pressure Problem ??

Just had a new water pump/impeller installed last year. The arrow/pointer on my gauge broke, so I replaced the gauge. It only reads about 2-3 lbs when starting the motor.

Then as I wait about 30 seconds or so to let it 'warm up' the pressure gets up to about 8lbs of pressure. While running WOT it will only push maybe 10lbs of pressure.

When I put the water gauge in, should I have blown air through the hose? I did that with my speedo and it fixed the problem there.

Is there any sort of filter or filling that might be clogged? Am I on the right track ? Any ideas are appreciated thanks !

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