I would caution you on using an Impeller pump <unless I misunderstood> for a Spray head like that. You will need a bleed off valve. If not each time you stop spraying the hose the pressure on the pump will burn up the pump, or blow a line.

I would use an aerator style pump to power the spray nozzle, or just connect it to a through hull and let the weight of the boat in the water force the water up the hose. Won't be as much pressure but works none the less.