The big reason is use case, environment, and mounting constraints. These engines are designed to survive 500 hours at WOT with nothing more than a few oil changes. The HP is also measured at the prop so that results in lower numbers than the crank figures normally stated in other industries.
Nah, little paddle wheels sticking out the sides of the hull that drive little generator units. Works just like hydro power!
I/O's are pretty old fashioned these days and a small block marine engine that makes 600 HP will survive for about 20 hours. Countless racecar guys dipped their toe in marine engines and most left with their tails tucked. It's a different animal when you operate under those sustained loads. Most 600hp marine I/O's are supercharged 502's running really low compression.
When I was a tiny lad my father taught the most important thing about boating. He'd make me repeat it every now and then, just I'd remember. He'd say, "What's the most important thing about boating, son?" I'd reply, "Never buy a Mercury, daddy." "That's right, son. Now go get daddy a beer." Many, many children of my era learned this crucial bit of information at their father's knee.
As a kid growing up in the San Juan islands where everyone had a boat, I can attest to this truth. I have a personal story about a Merc and a sudden deceleration of the crank that would have ended with... But we didn't have any. Luckily we had narrow floorboards and a flare gun. But Flare guns on the 4th of July don't really attract much attention. Unless (different story) it involves a parachute flare with an internal EPIRB. That will attract quite a bit of attention.
True enough. But it all comes down to use case. Putting around a 100 acre lake with no fuel dock? Electric range would be fine and no lugging fuel cans. More electric use cases will become a good choice as tech improves. Going to take a while to catch up with over 120 years of IC engine refinement, as one would expect.
Yep, a rite of passage in my town was getting a boat. Mr. Pierce of Fisher-Pierce lived in own town, so everyone had a Boston Whaler. The factory was only ten miles away until they moved it to Florida. Everyone went with Johnson/Evinrude, but is you wanted to put up with the BS, a Merc of higher horsepower was the way to go with a 13 footer. (40 HP max with a Johnson/Evinrude, 55 HP with a Merc.) A friend of mine stuffed a 135 HP Merc on the back of a 16' Whaler. It was scary to water ski behind that sucker at full speed. He named the boat "Black Power".
Interesting that steering wheels moved to the left on boats. All the boats I ever piloted or rode on had it on the right, with the control on the starboard side.