My grandson, he's 3 1/2, is the same way.
Loves going out on the boat.
Loves going fast.
Loves the sound of high performance engines, be it boats or cars.
Whenever I'm working on the boat engine or my truck he's right there with me, soaking it all in.
Turn on the Speed Channel and he'll sit perfectly quiet. Turn on cartoons and he'll get noisey with his toys.
I think it's cool.
I have the OSO main as my home page and everytime he hears that engine start he knows it's a boat and asks whose it is.