I have a 91' Sundance, "marin" model with a sentry 600 control box. I have re-wired the unit using 6-3 w/ground to get the full 50A, 240V power available.
It was originally wired with a 30A service **with a dealer modification to the circuit board**. How can I reverse this modification?

Darin

The 1991 Marin used an old CRL circuit board, there is a switch on the circuit board that will allow for a 50Amp service, however you cannot change the voltage going into the board. The second leg of the 220V needs to go to the heater only and then you can flip the switch (The only one on the circuit board) and it will allow the heater to come on whenever it wants.