Re: Boat Engines
Welcome to the WB Forum.
First, most boat designs have power recommendations. Indeed, many designs are built around a specific power plant. Is this a self-designed vessel?
You want to run AC power. How much? Once you determine that, you will need to install either a generator or an inverter. Propulsion engines produce DC power, but can by various means be used to produce some amount of AC if required.
Inboard, outboard? What does the design call for? Besides propulsion, where the engine sits in the boat will affect how she handles, drains, and more. This is one reason propulsion factors large from the get go.
Horsepower is horsepower. Its a value of the rate of work, and used to compare and rank engines. Torque is another matter. Torque is what actually does work. Its the force that turns a propeller. For a tug-- a real tug, whether diminutive or full size--an engine with more torque, to swing a larger prop is desirable. For faster boats, less torque, but higher RPM works well.
Do you want to go fast? Or slow? Both? Really tow other boats and stuff? Or just look the part? (nothing wrong with that). These are questions you have to answer.
Outboards produce less torque than inboards for the same horsepower, generally. Diesels produce more torque at the same horsepower than gas engines, generally.
This new ship here is fitted according to the reported increase of knowledge among mankind. Namely, she is cumbered end to end with bells and trumpets and clocks and wires. It has been told to me she can call voices out of the air or the waters to con the ship while her crew sleep. But sleep though lightly. It has not yet been told to me that the sea has ceased to be the sea.--Rudyard Kipling