?????? I'm unsure of your question. A 1 5 Grumman boat should easily plane with a 20 HP Mercury. If you have the rare "Jet Drive" rather than a propeller there may be other issues. My suggestion would be that you consult with a dealer. You might have different issues. Like only one cylinder is firing, or the drive is slipping.

Better yet, throw your propane tank in its mouth and shoot it with your .44 magnum. which of course all seafaring captains wear on their hip.
They hand them out when you get the funny hat and the funny shoes.
Just save the cabin boy !

The motor is the thing that cranks the engine, or raises the outdrive.
The public library has books about marine engines, databases, and can get books on loan.
Just don't drop them in the drink.
If you have an outboard, they have manuals for that too.
When i have used them it was the city library rather than the county library.

With a "regular" dc motor (there are several types subtly different from each ohter), you use PWM (pulse width modulation) which you will also find on the Arduino. This gives you control over the speed of rotation. Unlike a stepper motor, where you can control a partial rotation (one or more "steps"), with a "regular" motor, you can only get full rotations with no control over where in the spin the motor stops, just the speed.

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In pleasure boating the owner is often the Captain. However, once paying passengers are on-board , you must have a "Captain's License" All boats that are in commercial use require a Licensed Captain. You can still be an owner.