Since there is so many peoples been asking us how to do this, I decided making this tutorial
Car:
1) Make a car
2) Make a engine
3) Nocollide it and weld it into the car (the deeper the engine is in the car, the better the car will be)
4) Spawn a seat, connect it to the engine (just make it touch the engine) and nocollide and weld it into the car (make sure you can enter the car)
5) Make fuel tank, car battery, extaust pipe, radiator, turbo (on the engine) and car horn on the car (same way as number 4)
6) Make fuel guage, thermometer and car radio in the front of the car (so you can see it while you drive) and do the same as number 4
7) Add wheels (you don't need to edit values on the wheels, the engine pushes the car)
8.) Refill the engine with benzin
9) Add lights (front lights in the front, left and right dir. you know where to place and rear light in the behind)
10) If your car cannot drive, try reduce the weight
Boat:
1) Make a solid boat
2) Make a boat engine (propeller shall be directed away from the boat)
3) Make radiator, fueltank, car battery, turbo (on the engine), fuel guage, thermometer and car radio on the boat
4) Change the physics properties on everything to paper (to make it float)
5) Refill the engine
Using the stuff
Car Horn - Left Click
Car Radio - Reload
The Car Itself, dun-dun-dun-duuuuuuuuuuuuuuuuuuuuuuuuuuun!!!! :o - W, A, S and D
Start Engine - Space
Wrench - Touch the engine when its black (broken)
Steersense - For better turning
Tuning - For better turbo
The first guy who cries about the tutorial didn't help gets a CAKE 
