Are my RPM's to high

Hello,
I recently bought a new boat a 1995 17ft Starcraft with a 60hp Mercury 2 stroke oil injected outboard. The motor has been running great, but I'm curious if the tach is accurate or not. The service manual says that the motor should run at 5000-5500 RPM wide open, however it seems to sit at 6200 RPM when its wide open. The tach does seem to bounce around and some days its reading in the 5000 range, but mostly its around 6000. Im just curious if since the manual says that the motor should be at 5000-5500 if my tach is wrong or the motor is running faster and the tach is right.
I appreciate any input people might have.
-Spencer

Yes, no, maybe...

Sorry - if your prop is "too small", meaning you don't have enough pitch or diameter for the weight you are pushing the motor could be over-revving so the 6200 rpms "might" be an accurate reading.

OR

Your tach could be a little whacky, reading higher than actuality.

The WOT range in the manual is the range of "safe operation" based on how the motor was built/engineered. Exceeding that range could cause engine damage. Likewise, being "unable" to reach that range (as opposed to simply running at lower rpms) can likewise be hazardous to the motor.

Only sure way to confirm is to test with a "known good tach".

Thanks for the info, I guess I need to figure out what the actual RPM's are. Would the best way to just get a new tach. This whole thing came about because I was thumbing through the service manual for the motor and came a across a prop guide. Well the guide said that the prop I had on it was for a smaller boat, so I bought the prop that seemed more appropriate for the size boat, hoping to get a few more mph out of it. Well long story short, after I compared the 2 props this morning there wasn't more than maybe 100 rpm and 1 mph difference between the original and the new one. Now Im not sure which one I should use, the original one or the new one. I don't want to damage anything. Any advise you have would be great. Here is a picture of the prop guide.
Thanks
https://www.dropbox.com/s/16t7gsfqk5uoadq/IMG_20140920_153359327.jpg?dl=0