I have experience only with PWC pumps and not boats. I don't think there's much difference other than the reverse gate and steering linkage. Basically you remove the reverse linkage and steering linkage then you remove the hose clamp and hose that sits on top if the pump at 12 o'clock. Next are the 4 bolts that attach the pump to the hull and you slide the pump and nozzle assembly off the drive shaft. Your best bet is to purchase a shop manual and that will describe it in detail.
If I'm wrong on the procedure please correct me.