2004 Yamaha 225 4 strokes

[Purrfect]

I have a boat with 2004 yamaha 225 4strokes. When I put muffs on the motors and run water to it, crank them up, the water will not come out of the (pissers) but when the boat is in the water the (pissers) will function normally. What is the reason the (pissers) will not work properly while hooked up to the water hose with motor running?
Thank you in advance for any help anyone could provide!
Tray

[mitch]

not enough water from hose you need it in a bucket ..................................... dont run just on side connection as you will fry your pump