My Jet Boat Is Hard to Steer

Jet boats can reach speeds of 70 knots or more at wide open throttle. At 70 knots, their handling is superb. Unfortunately, you have to slow them down to enter a marina and, as you do so, the handling deteriorates until you feel as if you're sailing a bathtub without a rudder. That feeling will persist until you realize you are -- because your jet boat's motor provides all of its directional control.

  1. Life Without a Rudder

    • A jet boat doesn't have a rudder. While this might seem a disadvantage at first, the reasoning behind it is sound. The propellers and rudder are a source of subsurface drag in any boat, so equipped because they interrupt the hull's laminar flow -- the flow over a smooth surface. They also limit the water depth in which the boat can operate effectively. Instead of having propeller shafts, propellers and rudders beneath the boat, jet boats steer by directing the motor's thrust nozzle to turn or stop the boat.

    Jet Boats and the Third Law

    • Newton''s third law of motion states that "for every action there is an equal and opposite reaction." This is the principle on which every jet boat relies. Water is pulled into the drive unit by an impeller driven by an engine. The water is expelled under high pressure through an outlet nozzle. As the water is expelled to the rear of the boat, the boat moves forward. As the nozzle is moved left or right, the boat changes direction. When the jet stops pushing the water in a specific direction and the water flow from the nozzle stops, the boat continues to move in that direction -- no matter how much you turn the steering wheel -- because there's no rudder to change the boat's direction.

    Classic Jet Boat Understeer

    • Since turning the wheel has no effect when the jet's impeller isn't pumping water, you have to put the motor in gear to change direction. This means your jet boat will understeer at low speeds. You will turn the wheel to start the turn you want to make, just like you would in a boat with rudders or an outboard with a propeller. You may pull the motor into "Neutral" to let the boat coast to a stop. When you do, you can't increase the angle of your turn, unless you add power.

    Correcting the Problem

    • If you want to eliminate the steering problems, you have to learn to drive your boat all over again. You have to plan your approaches so that bursts of power, even at idle, can power you into place. You have to move your steering wheel in advance of the planned burst of power. Like the master of a large ship, you have to think and act in advance of need. This means practice -- always a good excuse to go boating, frequently -- to learn about your boat's handling characteristics both under power and without power. Then, to control your boat, you have to apply power in small increments to achieve your desired maneuvering goals.