What are boat engines/marine engines? How do they work?

Question

I just need a brief explanation. thanks:)

Answer 1

Marine engines are totally differant than automotive engines.
Marine engines have brass freeze plugs instead of an automotive steel plug to prevent rusting out .
The camshaft and valve springs are different due to the different rpm range a boat engine runs in .
The exhaust manifolds and risers are water cooled
the starter and alternator is designed to prevent spark to prevent a fire. The list goes on .
But it is coupled to either a outdrive or transmission which in turn spins the propeller. Pretty basic

Answer 2

How Boat Engines Work

Answer 3

Brief: As Yes says, mostly the same as in any car or truck.

Not so brief: Often they are just as Yes says, the same sort of engine you'd find in any car or truck. They work just the same, using gasoline or diesel to drive a crankshaft that makes the thing go. They do have modifications to the exhaust manifolds, and sometimes the cooling systems to both dampen noise, and prevent significant corrosion of the engine blocks from salt water. Marine engines, for the most part, use the water that the boat is in for cooling. Car engines do the same, but have coolant and a radiator. Some boats use a radiator too, but it's to separate the cooling water from the sea water.
People will sometimes look for replacement engines for their cars or trucks, and consider a Marine engine. This is usually a much more expensive proposition, simply because the engines are built to withstand the harsher environment of a boat.

Answer 4

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There are many boats now with 3 engine applications. Larger outboard powered boats have 3 engines for more horsepower, equals more speed. There are many ferry boats less than 100' with 3 diesel engines. Again this is because a third engine is needed for power not available with 2 engines. Modern engines of the type we are talking about all rotate in the same direction. In the outboards or inboard/outboards the lower unit makes the propellers counter rotate. In diesel or even gasoline inboard applications the marine gear makes the propellers counter rotate. The two outboard engines are used for slow speed handling (ie around the dock) and in some instances there is not even a rudder for the center engine. In many larger vessels twin diesels handle low speed propulsion and a gas turbine is used for situations requiring great speed. This turbine is normally conected to the diesel engine marine gears so there are only two propellers.

Answer 5

There are three basic Marine engines, same as cars, Two and four strokes gasoline , two and for strokes diesel and lastly electric, all of them except electrical, have some compressing element called piston moving tightly forward an backward inside a cylinder where a mixture of air/gas is compressed.
When the piston is at the maximum compressing position (top) the flammable mixture burns by meaning of an electric spark in gasoline engines or kinetic energy in Diesel, then the combustion gases expands to more than 120 times in some engines, this highly compressed gas push down the cylinder and rotates the crankshaft which is connected to some type of gear transmission to the propeller or a helical turbine which drives the water from the front to the back, moving in this way the entire ship, Electric motors (for fishermen) works closely in that way, but the propeller is rotated silently with an electric motor moved with batteries like the submarines or by an auxiliary electric generator

Answer 6

It may be easier to show you some pictures. The first picture link is an engine just like a car and the drive shaft turn a propeller instead of the wheels on a car.
The second picture is an engine that mounts on the back of the boat. If, you were to lay it sideways, it be almost like the first picture. Just straighten out the propeller.
http://www.yanmarhelp.com/images/boatexh.jpg
http://www.boattune.com/90OptiMax.gif

In the second picture you not see the engine as it inside the top cover, similar to a car, you have to raise the hood to see. ;-)

Answer 7

Either or. A third boat engine isn't used for maneuvering purposes, simply extra speed. if you have a boat trying to do 50 knots, and you need 750 hp, you wont be able to find two 375 hp outboards, so you use three 250 hp outboards.

Answer 8

A boat engine is the same as a car engine except instead of turning a transmission they turn a propellor.