Can't get pass 3000 rpms on my Mercury 60 4-stroke
A good place to start is with the basics.
Some have mentioned no spark in one of the cylinders. I'd pull all of your plugs out and look to see if any look different from the others. If you don't have spark in one cylinder and it is being dragged along for the ride, you should be able to see that in one of the plugs. Checking compression in all cylinders is also a good idea.
I'm with Muskie on this one. You should rule out low gas pressure. Partially plugged fuel filter, moisture separator etc.
Also, newer motors go into "safe mode" if they sense a problem (over heat, low oil, etc.) they limit the RPM to protect the motor. You usually get a ck engine led though.
Being a 2012, isn't it under warranty? Your dealer should not be putting you off until June, that is terrible service.
If you live anywhere near Lomira, give Josh at the Boat Doc a call. He is the best in the state on Mercury motors.
Hope you get your problem solved.