They all want a feed t'd off the raw water pump for speeds over 10 knots. You put a t after the raw water pump and feed it to the barb for positive pressure. The second t is to fee a second engine if you have one. If you dont you put a plug into it.

Tides, PYI also want one. Lasdrop says it's not necessary for slower speed boats but the recommend putting one in. At the very least, a vertical tube to purge air.