The duo propeller system uses 2 propellers instead of one.The propellers are fully submerged. The propellers are counter rotating. One propeller spins clockwise, while the other rotates counterclockwise. This reduces wasted energy and results in better efficiency through the water.
Explain the different type of gear selection systems (in outboard gearcases and stern drivers and Inboard marine gearboxes)
The stern leg system uses a tapered cone dog clutch system to select forward and reverse gear. the cone is pushed against the tapered surfaces to select gear. As the gear selector is moved the cone moves closer to the taper and then the two components are locked up together to engage the selected gear. The outboard gear case system on uses a dog clutch system which moves up and down the output shaft to select forward and reverse gear. I found the video below on YouTube which shows how the clutch dog moves up and down to select gears.
What type of gears are used in outboards and stern legs?
Outboards and stern Legs use helical cut gears which are in constant mesh. Helical gears are cut at an angle to the face of the gear. Manufacturers choose this type of gear because it is much quieter, stronger and smother. They can carry heavy load because of the greater surface contact with the teeth. As in outboards the gears are meshed at 90 degrees, these gears are able to be mounted on perpendicular shafts adjusting the rotating angles by 90 degrees. The teeth on helical cut gears are also stronger.
Why would a V drive be used instead of a standard shaft system ?
The V-drive system is a propulsion system for boats that consists of two drive shafts, a gearbox, and a propeller. Using V drive the engine can be mounted in the rear of the boat. In this system, the output shaft of the engine faces forward, and the shaft carries the drive to a V drive gearbox, which turns the drive through an acute angle and thus back toward the stern. V drives system can allow the boats to have flatter bottoms and are more roomy than standard shaft systems. The boat also have higher top speeds as most of the weight is at the rear if the boat.
Compare a jet unit with a surface drive unit and give reasons why you would choose one system over the other.
The jet system draws water from under the boat into a pump inside the boat, then expels it through a nozzle at the stern at high pressure which makes the boat to move. Whereas the surface drive uses propellers half in and half out of the water to propel the boat.
Surface drive is more cheaper to less fuel consumption than jet drive systems. Also the jet drive system sprays a lot of water out and get the deck messy. Jet drives are pretty inefficient at low speeds. Advantage of jet system is it has no exposed propeller therefore it can run around in shallow waters. But i was thinking you would not want to run them in shallow waters anyway as it would suck up sand into the pump and cooling system and cause damage. Also the jets can suck things up into the jet pump example plastic bags and ropes and etc and cause major problems.Therefore i choose the surface drive system over the jet system because of the above reasons and its simply surface drive systems are more efficient and cheaper to maintain than the jet system.
References
Once again, excellent work with good resources.
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