Took out our new to us 2003 Advantage Victory 28 MCOB. It has a 575 SCi, with the superchiller kit. Has a drive extenesion (which I think came factory) and a BR1XR Drive.

It's got a Bravo1 26P prop on it.

Granted, we were out in some pretty choppy Lake Michigan water...and I wish I would have documented better...
It seems possible I just couldn't find the right trim/throttle setting, or it was just too choppy but I feel the cruise speed to engine speed is way off. I was at like 3800ish to cruise about 40mph GPS. That seems like a ton of prop slip to me with a 26p prop.

I was not in boost at all when cruising this speed. In fact, if I were to increase the engine speed to increase the cruise speed, it would boost while I'm increasing load, but then back off when I'm cruising again. I'm pretty sure that's expected...

If I were to give it throttle it would damn sure GO, and pull like a mother! So, I don't think I have any issues with a spun hub or anything. And, the boost gauge would come alive when I'd gun it as well, so I don't think it's engine related either (plus it was just gone over and surveyed and everything was great).

I'm just trying to figure out if I'm just paranoid and it was just too choppy/needed to trim more and maybe change throttle a bit (learn how to drive it ), or if there's something going on.

Thanks In Advance!

I just sold an 05 model just like yours that I had for 5 years. Mine would cruise at 50 mph, 4000 rpm with a 28 bravo 1. Mine always had high slip numbers. Low 20's. Prop shaft is only about 4" below the bottom of the hull. I installed a 1" spacer and got it to hook up, but I broke a couple teeth off the upper gears with 700+ hp. Some times a little prop slip is a good thing

We cruise at about 80% of the top speed at WOT

spend some time in it in different conditions before you come to any conclusions about needing any changes...