The thought just came across my mind and I simply cannot think of a good answer, especially not knowing much about the mechanics of it all.
In: Engineering
There are engineering reasons for pusher props on boats and puller props on planes: weight distribution, what happens when cavitation occurs, turbulence and drag, etc. There are also engineering solutions to putting puller props on boats and pusher props on planes.
There is another factor: tradition. It is traditional to have puller props on planes. Ask a kid to draw a plane, and they will put the propeller on the front. When that kid grows up to become an aircraft designer, she will put the propeller on the front by default. Sure, she could put the propeller on the rear, but she has to sell that plane to the public, and the public wants a normal looking plane.
Planes get lift by pushing air onto the wings. The angle of the wings, which is adjustable on the fly by the pilot, determines how much air is put to use as lift (climbing) and how much is used for air speed. Boats don’t worry about lift, they just need to push water to propel the boat. Some boats have a rudder that controls what direction the water is pushed to turn the boat and others have the propeller itself turn instead (smaller boats use the turn propeller method, larger ones use a rudder).
Because flying is just swimming in reverse?
Boats also need it to be in the back to get on plane. Need the weight transfer to get the nose up. Think of a rwd drag car doing a wheelie.
yeah go look up [canard airplanes](https://www.huffpost.com/entry/why-arent-canard-style-airplanes-more-common_b_5a19b568e4b0bf1467a846e5?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAGyHKdRxgBkSwQrlamqQTSlmiOlekAYTJxkLAbw4B3Z0MvdOdd-6XJjctzHbCs_pzIryhrOZwqjZp4l91f5DyA0MDKf8dh-FKID_pquHpAK5u84qCZWaygw0YSTQnuQgU8ieLXNIgtwqG3Q2AZySrHDGU_fxdaJ_qR3O9xFdYzsp) with prop in the back
Airplanes normally operate in one state of matter – gas (air), though they use wheels to taxi around at airports between flights.
Boats operate in two states of matter – liquid (water) and gas (air) almost 100% of the time (outside of drydock).
While behavior of moving water (hydrodynamics) and moving air air (aerodynamics) share many characteristics, they do have some important differences. Water, for example, is essentially incompressible compared to air and is far more dense than air is -> this is one reason why airplane propellers and boat propellers are very different. Hydrodynamic behavior is also a reason why blunt shapes like modern submarines and bulbous bows on ships are common (much greater underwater efficiency) than the relatively sharper design elements on high speed airplanes.
Anyway, putting the main propellers on a boat up forward (along with maybe the rudders) also presents several challenges.
* Practicality. Propellers mounted forward on a ship would require the ship to have huge rudders back aft to provide enough force to change course (like, orders of magnitude bigger than they are now)-> huge rudders require massive machinery back aft to turn them -> massive machinery aft not only then requires compensation forward to maintain stability but it also limits the available weight and volume that can be used for whatever job the ship is being designed to perform.
* Safety. On the water and especially coming into port, is no such thing as the near-immediate stop on the water like you would taxiing an airplane or driving a car. Ships coming into port (unassisted) will typically make a slow approach and come close to the pier bow-first to put over lines and use their rudders and engines to bring the stern in. If those propellers and rudders were forward and there was a collision or harder than expected contact, then there’s a huge chance the gear would be damaged and suddenly a “hard bump” becomes a “boat drifting uncontrollably around other boats”. This issue also applies to hitting something uncharted (only 20% of the ocean is mapped) or just stuff floating around (like a log or a half-sunken container) as visiblity underwater is very limited.
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One of the cool things about aviation is some of the first planes had the engine in the back and the rudder in front or they put most of the weight in the back. The account of the first flight in 1903 happened as one of the brothers shifted his weight forward, so instead of an uncontrolable mess, the plane stayed off the ground. I think people designing planes like boats gave people the impression that no one would ever fly.
There are 2 additional factors i heard explained to me 20 years ago studying Aeronautical engineering:
Put the engine in the front, because if it crashes, you don’t want the engine to travel through the cabin (and the pilot). Aircraft crash in many orientations, but often nose first.
A propeller is subject to ‘prop wobble’, oscillation in the plane of the propeller. This is passed on to the drive shaft. A long drive shaft flexes / rubs against mounts more, and this leads to greater chance of failure.
Edit: had put vibration instead of oscillation
Take a look at the PT6A-66 pusher props. They are rear facing and one spins one way with one spinning the other direction to counteract the torque generated. This is not normally required for front facing props.
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