Change your technique, cure cavitation, and add air to the tube. I can get a tube with under 100lbs of people (less weight is harder) outside the wake with 4 adults in the boat (3 kids on tube).
Your tube should have 1-2psi in it. It should be VERY firm, and skim the water, not sink into it. The better inflated you can keep the tube the easier it is to get it to glide across the water. Until I bought a new pump this year I had to inflate it with a regular pump, then use my lungs to finish it off. Alternatively if you can get it inflated in the cool morning air, then let it sit in the sun, it'll warm enough to get a few PSI in there. It really helps make the experience better for both the riders and the driver.
Cure cavitation. For me, this was seal the intake tunnel for starters. I added an L13 cone as well, but just an intake tunnel seal is inexpensive, and yields great results.
Here's where I did mine back in 2018. Well worth the time and effort and the few dollars it cost. This really helped me maintain pump loading through turns. It's still not 100% cured, but it's MUCH easier to manage now. Not a silver bullet here, but a large improvement.
Change your technique. These boats don't like to accelerate AND turn at the same time. You want to get to speed (20+mph), turn hard over, let it bleed some speed, then accelerate out in a straight line. Think of the tube as a large pendulum. You want to put a pulling force to accelerate the tube slightly. The rope is uncapable of transferring side loads, only tension. So as you accelerate away, the tube is swung over the wake as it attempts to create a straight line with the centerline of the hull. A large sweeping turn at speed, then a quick burst of straight acceleration, and back into a sweeping turn will "pull" them straight, and outside the wake. Once they are out at one side, use the change in direction to "swing" them back to the other side. It's a CONSTANT, slow and speed pattern with acceleration in a straight line, and sweeping turns elsewhere.
Likewise these boats are exceptionally sensitive to bow loading. Get your people to sit in the rear during tubing sessions if you can. Get as much weight out of the bow as you can reasonably so. You will align the angle of the hull (and the angle of the thrust) more directly with the direction of travel. Because these hulls are so short, when you get people in the bow, the nozzle gets an uphill angle to it. This causes the bow to "plow" more than you want. Great for a smooth ride, NOT great for transferring power from the jet to forward movement. A few weeks ago it was myself (225lbs), my wife (135lbs), our 10yr old (61lbs) our 3yr old (40lbs), and my mother (~300lbs). I was driving, 3yr old and mother in the boat. Wife and 10yr old on the tube. First pulling session SUCKED, it was a lot of work to get them outside the wake, had to really work on my technique and was a constant struggle to fight off cavitation and maintaining drive in the turns. Second session was AMAZING. Seriously, it's like it picked up 50hp, and had tons of traction. Like a completely new boat. Tubing was easy, I could quickly spin them out of the wake, and I had to be careful to NOT break into the 30's, as the boat just felt like it was running so well. The difference was moving my ~300lb passenger from the center front bow and 3yr old from the port bow seat, to the port rear seat and center rear seat. Just that location change of 340lb made an almost indescribable difference. I can't preach enough on how sensitive these hulls are to that bow loading.
I've got more stories that illustrate the same thing over and over. Keep weight out of the bow, and you'll get better performance. These 19ft hulls are exceptionally light, relatively short, and have exceptionally light drivelines that "people ballast" makes up a LARGE percentage of total weight, and that can easily throw off the balance of the system and lead to poor performance........I REALLY REALLY want to try putting a trim system of some sort on this boat to mitigate these issues, but haven't taken the time or effort to make it happen.
@SamCF did it here with great results, but it's on a supercharged boat. I'm unsure if anyone has done it on a normally aspirated 19ft'er yet.
