Another thing to note is that because the jet boats don't have anything really hanging below the hull, like traditional I/O boats or any hydrofoils, they can turn significantly harder and tighter, which means you bleed off more speed as you turn harder. I've gone 40mph and able to hold my speed in a wide turn yet, at the same time, can do 40+ mph and yank the wheel hard left and I'm pretty much drift the boat before "spinning out". Tiz the nature of the beast.
Also remember that steering is based upon the direction of the jet nozzle, not a rudder or some fin underwater to keep the steering tight. I, as well as others, have thrust vectors installed to help with stability but primarily at lower speeds as the fins are spring loaded and lift up at higher speeds. But even then, just to maintain going straight, have to put in a lot of steering input. Don't have to, but it's a bit fun for me to do so. But the turning characteristics essentially boil down to HOW jet boats move forward and turn. In general, water is pulled not completely straight up from under the boat, but from bow to stern direction, creating a pulling forward motion. The water shot from the nozzle also helps move forward as well. But, when in a turn, water isn't nicely forced along the forward direction anymore and at an angle, which reduces how much water can be pulled in and needs to be compensated with more throttle. And why the harder you turn, the greater the angle water is pulled in, and more power is needed. This is also why when I turn crazy sharp 180º +, I essentially stop. Water is pretty much flowing in the opposite direction from ideal that no matter how much throttle I give it, it won't be enough, especially with the change in momentum.
Back to the whole water should be flowing from bow to stern, it can also be a corrective force to help the boat go straight, especially at higher speeds, but the keel kinda does that on its own. But, by "fall out" of turn, where you turning left or right? When I turn left, it's effortless. When I turn right, the boat fights me a lot more and starts listing a bit. The more weight or people I have, the greater the resistance to the point I just hold going left till I go in the same direction I would have gone going right. That characteristics is relatively common. I do have an issue with my thrust vector bracket on my starboard engine that may be worsening the behavior in my situation. If you're describing overall general moderate turning and feeling some speed bleed off, totally fine. With everything I said, don't try to compare a jet boat to a car. A jet boat would be a car driving on ice, you don't really have "traction" to help you maintain speed in a turn and the boat is just sliding in a turn, which is the thrill of having a jet boat!
