Comments by "Keit Hammleter" (@keithammleter3824) on "History's Most Punishing Naval Battles" video.

Both oars and propellors have an energy transfer efficiency of about 82 to 85 percent, so it would not have made any difference on that basis. Propellors offer simpler transmission from a rotatory engine. One might visualise crew turning a crank shaft, much like turning the sail cranks in a 12 metre yacht. However this means only the arm muscles are used. With oars, using movable seats, you can use both arm and the more powerful leg muscles, so oars are better with human power. In the magazine Scientific American about 40 years ago, there was an article written by some university boffins on the effectiveness of oar-powered triremes - they concluded that with experienced crew of modern sports fitness, they could at a pinch get the vessel up to planing speed. Not for long though.
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@toddcytra I should have thought of pedals - but pedals only utilize leg muscles, whereas oars can utilize both leg and arm muscles, giving greater power. Propellors are kind of hidden away, but if they had used propellors before the age of guns, a countermeasure immediately suggests itself - a steerable net dragged behind, to snag the enemy's propellor. If a side collision was immanent, I expect that galley captains would have called out "Ship Oars!" (i.e., pull them in), otherwise an awful lot of oarsmen would get broken bones (including smashed ribs) and torn muscles, making the ship a cripple.
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