
....and that just let jet thrust escape thru there instead of pushing the boat forward.....
ive heard it can also be used to control the amount of thrust going out of nozzle and thereby controlling how fast the boat goes. for bracket racing. can be set in a comp to do so automatically at a given point and how much to open valve. less things for the driver to worry about while making a pass.
i havent heard of it being used as a brake, if you will.