Buzzer...
The 92 SP does not have the DESS. THe buzzer is likely your temperature sensor. Probably bad.
You said you were able to turn the motor over, but not fire. Chances are, the tether may not be making the circuit.
Because your ski is so old, I haven't read a lot in this manual.....if you know how to check continuity, check your start/stop switch and your lanyard switch to see you get an open and closed circuit.
Let us know what your results are, in the mean time, I'll go through the manual a little more to see if I can help you out. Be careful working on your electricals, they can be shorted if you remove wires and hook them up with the battery connected. I haven't read about your module and what type you have, but I'm sure you got one and that will be what cost you if you blow it!