I can't get above 4700 rpm w/ 1993 Johnson Silver Star 150

[bassoneer]

I recently damaged a propeller, and instead of fixing it I decided to change it because I had not been able to get above 4700 rpm fully loaded. I have a 1993 Stratos 274FS (17'-9" fish and ski) with a 1993 Johnson 150 Silver Star V6. I switched prop size from a Shooter 13.25 x 27pp to a Raker 14.5 x 22 pitch. However, when testing this weekend with the new prop, I remained at 4700 rpm...speed went up slightly from 45 to 47 mph (gps). So, somebody has recommended I check my motor, because the rpm's should have jumped up with that prop switch. Any ideas what could be wrong to limit the rpms like that?

Thanks, B

[ELGIN]

Have your tach checked, may be reading wrong.