"I would find out if it's
"I would find out if it's propped correctly but I'm also wondering why you're asking here. If the specs state 320HP @ 5200 RPM and you're maxing out at 3600, there's either a fuel, prop or electrical issue. Call your dealer and ask the questions they should have given the answers to at the time of sale and delivery. There's no reason you should need to ask now when they should have already covered break-in, performance, warranty, etc.
The HP @ 5200 is likely the maximum and while it's nice to see a big number and they often sell boats by posting the biggest number without really using a practical context. Unfortunately, HP and torque curves are really hard to come by so unless you have an "in" at Volvo-Penta, Mercruiser, Indmar or some other place where they actually test the motors, you're not going to find it. I was a marine tech and trained by Mastercraft's trainer, who is extremely knowledgeable, well-connected at GM, MC, Indmar and Delphi and he couldn't tell me because of confidentiality agreements but I also have a fiend who worked in V8 Powertrain Development at the GM Desert Proving Grounds and he asked but couldn't get me any specs, either. Suffice it to say, the curve isn't flat but if it's TBI, there's a hump at the low end and it flattens from there. If it's multi-port, it doesn't have the hump but is broader and flatter. The curve generally rises as the RPM increases. How flat/smooth it is, depends on the programming/carb setup.
3600 is low but I would finish the break-in period before condemning it."
