I recorded quite a few powerboats as the passed by - but getting usable game audio is quite tricky. I'll tell you why:
First of all, there is a PA system with an announcer that feels obligated to speak non-stop which is great for the audience but terrible for someone who wants to capture the boats and nothing else. I had to find a spot close enough to the boats, but far away enough from the diesel-powered speakers pushing out a distorted commentator voic.
Then there is the audience, they tend to chat and cheer a lot so I had to find a spot far enough away from most of them - luckily the powerboats are loud so the gain is not set too high which reduces the chance of spectator voices.
Another challenge is that you don't really get that close to the boats, they have to drive where it's deep and safe enough which isn't always that close to land.
The splashing water is another parameter to consider, but again, not loud enough to be too great of a problem.
The biggest problem, however, is that the boats pass by producing a sound that fades in and out and shifts in pitch due to the doppler effect. By default they will be great if you want to have the sound of a passing powerboat - but you could never apply that sound to a boat in a game since it simply doesn't loop well.
Turning the passing powerboat sound into looping game audio
I put together a video where a single powerboat passing by is turned into a short loop of game audio that could be used on a powerboat. If you need to do something similar, or if you are just curious what work goes into converting the sound, have a look:
I ended up using the audio from the Rode NTG3 shotgun mic this time since I didn't need it to be stereo and it produced the longest sustainable sound as I aimed the microphone at the boat as it passed by. It also contained the least polluted sound since the design of the shotgun mic blocks off-axis sounds fairly well.
This sound loop, among many others, will be included in the next update of the Universal Sound FX library.