Water pump flow

[Burlington1]

I recently had new water pumps, thermostats, sensors, and popit valves replaced on my 1996 150 TXRU and am experiencing a water flow issue at mid-range rpm activating the sensors due to temp increase. no issues from idle to 2700, or past 4000 rpm, however, I loose flow in-between that range. I flushed the motors with salt away thinking it might be a crud issue.....Any thoughts???

[pstephens46]

20 year old motor. It very well may be partially clogged.

[99yam40]

do some research on Rydlyme marine descaler, some have reported good results.
it that does not help then pulling heads ,covers, and exhaust plates to manual clean

[rodbolt17]

has anything been added to the hull?
are you sure the water screens got installed properly?