Top speed struggle on '18 GT185 after winter storage

[fiberglassflash1022]

Last month, I took my 2018 GT185 out of storage and noticed something strange, the top speed is now stuck at 42 MPH. Last season, it would easily reach 50. It's got the same 4.5L 200HP MerCruiser, the same 19-pitch prop, and I'm on the same lake. I even checked with the GPS, and it confirmed the speed drop. The boat seems to handle fine otherwise, but the limiter kicks in at 4800 RPM.

Could winter storage have caused this issue? Has anyone else experienced a similar slowdown after some downtime?

 

[CAPEESH]

RPM with that speed suggests the engine is working harder to push the boat. Is the bottom of the hull completely clean of any marine growth? Even a thin layer of algae is enough to reduce your top speed (by a lot).