Very loud continuous beep sound

What year, what engine, what outdrive??? Does the beep continue after the drive oil reservoir was topped off?? That is where I'd start. There is a low fluid sensor that can go bad as well

 

MPI or EFI? Could make a difference. Stock would have been EFI.

 

Sounds like the computer is putting the engine in guardian mode as a result of input it does not like from one of the sensors. I hear tell that the low oil in the stern drive can do that.

 

This was my original thought too but the "everything is fine until 3500 RPMs" statement kinda threw me off of that.

 

Agreed Mr. M-
If it is not the oil in the stern drive, then something is putting the motor in guardian mode.

Either the dealer's scan tool or one from Rinda are probably your best friends in diagnosing this.

 

Connect CDS to determine
and diagnose the problem
5–90% available power
dependent on actual fault.
Guardian is active!
Guardian strategy
Over speed
ECT overheat
ECM memory
Multiple CAN Circuit faults
EMCT overheat
Engine oil pressure
Battery voltage

Copied and pasted here:

 

Well, I was hoping you had made a mistake when you said MPI. EFI is much easier to diagnose over a forum as it's a simpler system with less sensors and a less sophisticated ECM. As you've probably come to realize by the above comments, the most productive course of action is going to be getting a scanner hooked up by a Merc technician (doesn't have to be at a Sea Ray dealership). Even with the MPI systems, there's been changes made over the years to the programming, which again, makes it more and more difficult to diagnose via a forum. Best bet... let a trained Merc tech look at it. Otherwise you'll likely spend more money (and certainly time) by guessing and throwing parts at it.

 

If you still have the alarm after filling gear lube I would simply disconnect the wires underneath the reservoir. If the alarm goes off there is your problem. I have had the reservoir float stick in the down position after filling.

 

Hi there, if you have not solved your issue yet, check the shift switch as if this has failed it will be telling the PCM that the motor is in neutral and will not let you rev beyond 3500rpm. Good luck

 

If a Smartcraft display was added, would that indicate what the issue is? I have an EFI engine so I'm not too familiar with the Smartcraft capabilities, but I think that it would.