It's a 150. Rpm at wot is around 5600 when on pad. Getting on pad though it just drags around 2800-3000 rpm
You say the boat started this and has gotten progressively worse over the past year. When it wasn't having an issue, what was your RPM once on pad? What's the recommended max RPM range for your engine? (Remember, lower than recommended at max is not a good thing - it assures the boat is strained and poor performing.)
Has the prop been changed? Do you recall any solid obstruction hits with the prop?
Have you ever changed the spark plugs, fuel filter, or done any of the other proper maintenance on the engine?
On the spark plugs, if they've been changed, was the EXACT recommended plug used? Has anyone with expertise pulled the plugs to look for signs of a dead/misfiring cylinder?