William R. Watt wrote:
Any opinions on the feasibility of foot-operated water jet propulson for a
small boat like a canoe or kayak? I was thinking of mounting twin water
pumps on the (out)sides of the hull to suck water in the front of the
pumps and squirt it out the back through a smaller diameter pipe to make a
jet stream. The water pumps would be foot operated through levers and a
pivot. Got the idea from reading a book on ancient Roman engineering.
Could the legs and water jets produce enough propulsion to move the boat
at, say, walking speed? I think a separate pump on each side, powered
independently by the two legs, would allow the operator to steer the boat
by pumping one harder than the other to turn.

That's what paddles are for. Simple, elegant, effective engineering. I
don't understand why people are constantly trying to "update" the basic
design of these elegant craft with "Rube Goldberg" mechanical
mechanisms. A large part of the beauty of these boats lies in their
simplicity and the connection that the paddler has with the water. To
eliminate that is to change the very nature of the boat.

While your idea could certainly propel the boat, there are at least two
problems with it. First, the operator would still need to carry a
paddle, as it's necessary for turning and in the case of a kayak, for
bracing and rolling. Second, your system would not work for anything but
the gentlest of turns except perhaps on a really short boat. There
simply wouldn't be enough of a lever arm to cause the boat to turn abruptly.