2002 Johnson 150 Lost RPM

I have a 2002 Johnson 150 J150PLSNF. Normall WOT is 5500 rpm but it is now only turning 4800. Had my mechanic look at it and he checked the compression and said it is was real good, and said the plugs looked good and thought it might be the VRO. I took it out this weekend and when you hit the gas it will surge once or twice like it wants to go but then just settles in at 4800. I pumped the bulb each time before I would take off and it was always tight.

Any ideas? Also If turns out to bet the VRO what kind of $$ am I looking at.

Thanks

Suggested list price is $395.00. I would ask the mechanic to test your fuel system. Make sure your carb plates are opening fully at WOT.

Power pack?

Well just got the boat back and it was the Power Pack.