Im am pretty much an outboard guy. I recently bought an immaculate 2005 Formula 260 Bowrider. It has a 496 (not an HO) with a Bravo 3 outdrive. Motor has 500 hours from new and the entire boat and motor is immaculate and freshwater only used. Boat runs around 52 MPH+-. As a rule of thumb with outboards, I have always used 12-15HP upgrade per MPH. What are options or changes if I wanted to see 65MPH out of this hull?
How much HP can a Bravo 3 Handle?
Do I supercharge what I have?
Do I find a 525? Can I use existing drive? What do I need to do with exhaust?

I dont know anything about that particular hull... but I'd venture a guess and say you are way off with the top speed. Has to be something not running right or out of tune.

I have a 2007 Chaparral 256SSX with the exact same engine (Volvo Penta 375hp) and it has been 55.2 mph on the Garmin GPS... and my boat is not made for speed. At all.

That's an accurate speed for that boat/engine combo. Heavy boat. Matches what my '04 Chap 260 SSi ran with same combo. Again, mine was a heavy boat. Would sink my 6K lb lift if boat was full of gas and I stepped up onto the boat.

My bad then. I thought the Formulas were faster hulls than that.

I own and build 496/8.1L engines, but in your case I would put a 525 in it. It's a much more common platform. The 496 is fantastic in stock form, but the aftermarket parts availability and knowledge just isn't there compared to the 500/525 platform.

I operated a buddies Formula 260 with 496, unsure if mag or not. Never payed attention to top speed as was just a designated captain.
That thing was a slug all around.

Yes, a buddy had one and they are a big ol girl!

The hull for their runabouts is very similar in design to the Chaparral hull. My boat hit 54 MPH GPS once and that was on an early March day, some wind to get a nice ripple on the water, very little fuel, just me, and no gear in the boat. Most days with a normal fuel and gear load it was a 52.xMPH boat. Your current ride is doing well considering the power.

Weight on these production boats is all over the map. Had a buddy that worked at the local Rinker dealer and he installed a lot of thru-hull exhaust after the fact on boats folks bought that it didn't come with from the factory. He kept all the fiberglass cutouts on his work bench from these jobs. It was amazing how much they varied in thickness between boats and even from port to starboard on same boat (these were out of the side of the hull). I swear on my '04 Chappy they accidently kicked over a 55 gal drum of resin in the hull when they were laying it up.

280ss run near with that twin 350s. Just upgrade, you’ll be money ahead.

I have introduced many, many people to boating over the four-plus decades I've been in the sport, and I always, always tell a person considering a purchase to buy the most power he can get, as it is never enough, lol. So many times I hear something like this, "Man...I love this boat...just wish it was faster...".
You could go drop $20K - $30K into your boat and get the speed you are looking for, and if you love everything else about it and plan on keeping it for a while, that might be the best option for you. Or you could sell it and, as hogie roll, notes...just go buy a faster boat.