The propeller as well as the forward motion of the boat pushes
water up the intake tube. This same forward motion creates
suction as the water passes where the water exits. Gravity
also helps the waters exit the motor. To get the water circulating
you should immediately go to full throttle. Then you can slow
down if you choose, checking the cylinders to be sure water is
circulating. For this system to work properly, especially at slow
speed, there cant be any air leaks. The motor above, I posted a
picture of, cooled well at every speed.
Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.