tom kane: Kit set Boat c1900 Tunnel Drive.

The propeller is in a tunnel has its axis above the waterline at rest,its blades protected from grounding.When moving forward the tunnel fills with water and the propeller works properly.A large horizontal flap at the back of the tunnel floats up to allow the propwash a clean exit.but on going astern it sucks down to prevent air entering. www.whanganuiriverboat.co.nz www.focusnzphoto.co.nz