In a classic speedboat, the engine is housed inside the hull rather than hanging off the back. This approach comes with a lot of complications, but it looks better, in my opinion.
The easiest view to draw is from above. Let's start with the hull: two symmetrical curved lines — the sides. The transom is angled, so it's visible.
Next, let's add some details: a windshield, a seat, and a steering wheel.
You can also add fins at the stern.