what is this?

[wavehummer]

what is the hose that goes from (I guess it's the pump) to the top of the steering nozzle? on the back of the ski

[Dr Len]

I think the hose you are refering to is the hose for the OPAS. It comes off the pump and goes to the diverter valve
for the OPAS.

[Shibby1485]

dr. len is right.... those hoses have water pressure in them. when your ski gets into high speeds (max pressure) the water in the lines gets under such intense pressure that it picks your OPAS fins up. when the ski loses pressure, the OPAS funs drop down. only the seadoo 3-seaters do this.