So does the N1 and N2 require seperate levers or is it automatic?
In a helicopter n1 is the throttle. and n2 is the rotor speed.
These are both adjustable by the pilot.
Throttle and Collective pitch.
The rotor increases and decrease pitch in turn starts to pull the rotor
speed down . There is a droop compensator which keeps the rotor
speed up in the event the pilot has a heavy load Ex, lifting logs etc.
In a boat the n1 is the throttle and n2 is locked down at a given setting.
In one of my trial runs we could not get the boat over 100.
The n2 was locked down to low. simply backing out the stop screw is
all it takes.
Now you could certainly run a throttle on n2. this would give you
two throttles on each turbine.
In caution one needs to remember the n2 control is the actual governor
of the rpm. the maximum rpm of this is roughly 23,000.
By pulling back on this lever as in leaving the water would never
slow it down quickly enough as not to cause a overspeed.
Hope this helps