I have 2004 BF115HP and still getting lower water flow than think I should at tell tale. I no the T- fitting isnt clogged, but the water lines themselves "could" be. I just replaced the impeller and when I pull the T-fitting the water is gushing from the main hose so I know the pressure is good. I am getting a light flow from the tell tale but I needs to be stronger. I am connecting the garden hose at the flush port just below the cowling in the back of the motor (not the ear muffs) if that makes any difference.

 

Sounds like a blockage, someplace.

 

I had bee's build a nest in the outlet hose cooling box which caused this problem. it happened in two weeks while boat was sitting. Hope this helps you.