@EternalDarkness Dart fins are good for going straight, but without additional surfaces amidships it is difficult to change vector without a lot of slide and wasted effort. It can be done with thrust vectoring, like on outboard motors, jet skis etc. But without the simulation of the hull cutting the water, options are limited.

@ThunderscreechEngineering You can probably make it turn even tighter if you put the engine on a rotor that steers. That might not be practical or realistic, depending on the boat.

@F104Deathtrap read below

@ThunderscreechEngineering no problem. The thing with the keel that someone mentioned is to give lengthwise rigidity to the ship. But, like on planes, surface providing longitudinal stability must be at stern, like fins on a dart.

@EternalDarkness Adding two extra stabilizers helped a lot, and now it is actually usable. Thanks!

@F104Deathtrap That, combined with a changed rudder rotation, seemed to have helped. However, it still drifts.

@EternalDarkness A) One short one that runs the whole length and has a large control surface at the stern like large ships or B) Two large fins, one halfway back from the prow and another at the tail to be used as a rudder as per smaller vessals and fish.

If it has to propellers try setting the power for them to trim and VTOL and alternate trust
Aka reduce the left prop to turn left

You need a very big vertical stabilizer near the stern. Or multiple stabilizers.

Try running a short (y-axis short) wing along the centerline of the bottom of your boat. This is called a keel and it might help.

@Tully2001 Yes

Yeah,the water physics are pretty bad.It happens with all of my boats too.Try putting a gyroscope set to yaw on it.

Put a VTOL nozzle on the front of the boat, just above the waterline. It needs to face upwards. That won't fix it completely, but it will help greatly.

That’s because of the water physics.