Esp package should get you 46 to 48. If it's a bowrider, then speed will be less. I hit 46 with a 23rsb elliptical center toon and a yamaha 300. I think I could get a little more mph our of it by raising the motor, but I would lose bite in turns. I'm happy with where I am.
Michiman is right. Something is off. Frankly, way off. But through a pretty short list of process of elimination, it should be somewhat easy to figure out.
In addition to the info I asked you to post above (RPM’s at WOT with MPH)*, also share:
What prop you have (brand, size)?
What hole is your motor mounted in?
*Also, ideally when recording your speed/rpm numbers run the boat at a lighter load, maybe only 1-2 people, no gear, half tank or less of gas, on fairly calm water.
You posted it is a 2018. Have you owned it the entire time, or a new to you used boat? If you have had it this entire time, has it always performed this way?
Also, how clean are the pontoons? Pics?
Does it “list” slightly in any direction? Any “sloshing” sounds from pontoons when on a trailer?
Can you verify the guess above for hull (ESP?) and underskinning? I too am assuming it has both too, but just looking for verification.
Anyway, your performance is way off from where it should be. By getting answers to all the above a lot of very smart and experiences people in this forum can help narrow down what’s behind these very low performance numbers.
My main guesses: wrong size and prop, and/or dirty pontoons. However, I couple other things could be in play as well, hence the questions above.
My 2017 23RSB with ESP and yahama SHO 250 would run 46-47 with two people on it. Adjust your trim and see how much difference that makes; if you have the front of your tunes in the water you are just plowing and wasting gas.