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Engine Operations and Propulsion

Updated: Jan 22, 2022

Engine Operations and Propulsion … Regardless of their size, your boat’s engines are part of a complex operational system that propels your vessel, and helps the Skipper navigate his or her boat through all types of water and weather conditions. This boating safety tip will address the different components included in the engine’s propulsion system, what their function is, and how they help Skippers influence their boats while underway … 1. Rudders … Rudders steer the boat. In order for a rudder to work, your boat needs to be underway. This creates a flow of water that passes along the rudder‘s surface. The Skipper can change the direction of this flow by changing the Rudder’s direction using the ship’s helm. The Skipper uses the helm to turn the boat from port to starboard. However, a boat with rudders will react much more predictively when the throttle is in the forward position. Be aware that rudders are much less effective when the throttle is in reverse … 2. Propellers … The propellers are attached to the engine’s crankshaft. The main function of the propeller is to push the boat forward through the water. However, when backing up, the throttle is in the reverse position and the propellers pull the boat backwards … 3. Right Hand and Left Hand Propellers … These are used by vessels that have two engines that operate in opposite directions. This configuration is called … 4. Counter Rotation … Boats equipped with counter rotating engines (and associated props) are much more maneuverable when backing up. This capability is especially useful when docking. With practice, a knowledgeable Skipper will be able to back the boat into a slip while using the counter rotating engines to maneuver the boat without using the helm … 5. Pitch … When you look at a propeller from the side you will notice that the blades are twisted. This twist is called the pitch of the propeller’s blades. In ideal sea conditions, pitch is the distance a vessel will move forward with each rotation of the propeller. For instance, a19 inch pitch will move the vessel 19 inches forward with each rotation of the propeller … 6. Diameter … Diameter measures the prop from tip to tip. “Diameter is determined primarily by the rpms the ship’s engine can achieve. If you want your boat to go fast, smaller diameter propeller should be chosen. If you have a large, and slower commercial or recreational boat, a larger diameter propeller is preferred. 7. Prop Walk … When a propeller turns it pushes the water astern, but some water goes to the Port or Starboard as well. As you might expect, this propulsion toward the side of the boat moves the stern to the Port or Starboard. If you have counter rotating propellers the Skipper can correct for this sideways movement. However, with a single engine boat backing becomes quite difficult when you need to move backwards with precision. As a rule of thumb, a propeller that spins in a right hand direction will move the transom to Starboard while a left spinning prop will move the transom to Port … 8. Single Engine Boats … It is important to know the differences between single and twin engine boats. While a single engine boat has only one propeller, that propeller may spin in a left or right direction depending on the boat's throttle position. In this configuration a right hand spinning prop moves the boat forward while pushing the transom slightly to Port, If the engine is backing while rotating left the transom will be pulled to Starboard … 9. Twin Engine Boats … Boats with twin engines have a significant advantage over single engine boats. This is because boats with twin engines have counter rotating propellers. This means one engine spins in a left hand direction and the second spins right handed. It is these characteristics that enable twin engine boats to be skillfully maneuvered in close quarter situations. This is especially true when docking … 10. … Single Engine Boats … If you are onboard a single engine boat and the engine stops, your boat will drift until it becomes dead in the water … 11. Twin Engine Boats … If you are on a twin engine boat you can proceed under power even when one of the engines has experienced trouble. In this situation you can proceed with either the Port or Starboard engine. However, be aware that since only one engine is running and it is not centered on the transom, the boat will turn in the direction of the disabled engine. This imbalance can be handled by the helm. So, if the Starboard engine is running, the Skipper must compensate by turning the helm to Starboard to stop the boat from turning to Port … 12. A Best Practice … When your propulsion shuts down Follow Your Float Plan !!! A float plan includes a description of your boat, who is on board, and a description of the safety equipment onboard. Also, identify where you expect to be, and when you expect to be there. Most importantly you should include a contact number. You can learn about Float Plans by consulting the US Coast Guard’s recommendations at ...

Remember … Smart Boating is Safe Boating

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