how much water should an alpha gen II push to the therm housing?

[2004 searay]

i have a 1990 4.3 merc and its overheating. i replaced the thermostat, manifolds and the impeller assy. the water flows to the therm but not a heavy flow, i know it is pushing water through a 3./4" hose to a 1" so the flow should be less but im still thinking it may be an issue. otherwise i am kind of stalled on what it could be

https://photos.app.goo.gl/1iKrXr4EGnwrh6hg6

 

[Bt Doctur]

if you remove the inlet hose is should squirt up about 6-8 inches

looks like you need an impeller