2004 Yamaha F115 Power Issue

[Mrcobia194]

Hello all I have a 19ft Cobia with a 2004 Yamaha F 115. I just bought this boat about a month ago, it has a 17-k painted ss prop. I changed the plugs and oil, and resealed the lower unit, the engine seems to be running smooth no shaking, or stalling, starts up fine, but out on the water with just me and gas on the boat it will only run 30mph top speed trimmed at 5400 rpm WOT. Ive been told to change the fuel, clean the injectors, only use rec-90 fuel, clean the VST, check fuel pressure, check compression, etc. Please help me on this matter where should i start because that is a lot of stuff to do considering I really don't know if that is the Problem... Any help would be appreciated. Thanks

[rodbolt17]

before you start.
find a dealership with test wheel YB1624.
that F115 should spin that wheel about 5800 RPM.
if it will you have a hull/prop issue.
if it wont you have an engine issue.
this may save you a lot of time and money.
chasing ghosts gets expensive.