The Inboard/Outboard Problem
Many years ago I used to spend a lot of my time messing about on and with boats.
Boating has been described as standing in a cold shower, fully clothed, setting fire to hundred dollar bills. In retrospect, this is not entirely inasccurate.
One of the most expensive bits in boating is the contrary beast "the motor". This is a complex combination of infernal combustion engine, flammable fuels, delicate machinery, and electricity, all immersed in dirty salt water and operated by an amateur. It works about as well as you might expect, from that description.
Motors on boats come in two major flavors: Inboard, where the entire contraption is enclosed within a part of the boat called a bilge. (The bilge is where all valuable and important parts and tools gravitate towards, and is not complete without a few inches of evil-smelling salt water/oil mix at the bottom).
By contrast, an outboard motor perches precariously on the transom (back-most bit of a boat), with most of it's machinery hidden by a large fiberglass cover.
Each style has it's advantages and shortcomings. An outboard engine, for example, may be more accessible, and can, at the correct point, be jettisoned entirely by merely loosening a couple of clamps. The outboard has a bit called a lower unit that has the propeller attached.
An inboard engine, on the other hand, has it's weight placed lower in the boat, and be used as ballast when frustration reaches the point where you want to sink the whole thing. It has a complexity an outboard does not - there must be a place where the shaft the engine turns exits the boat, via a mechanism generally regarded as harmful to boats, namely a hole.
In 1948, Mercury Marine engineer Charlie Strang mated an aluminium car racing engine to the lower unit of an outboard motor, creating a marine propulsion system more powerful than the outboard motors available at the time.
Over the years many variations of this approach were used in a great many boats. Boaters generally being a bit slow to learn, the style is still in use today.
As with many things in the software business (see, we were coming back to that), the inboard/outboard engine has the unique property of combining all of the negative qualities of two different designs, adding only minor benefits, and adding a few unique problems all it's own.