J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Warm starting problem. Anyone run into this problem ?

He means the ignition key switch, but the master battery switch will also cause a problem. Don is correct - always shut the engine down with the fuel cutoff.

Using the key switch open circuits the battery from the charging circuit. In EE terms it tries to cause a rapid di/dt and since the current can't change instantaneously, the windings produce a voltage spike that can fry the alternator diodes.