That could depend on the failure mode, for example if its a shorted input, that could tend to heat up stator winding's.How much is too much? IDK. If it went into a un-reg'd output failure situation, this could allow excessive output voltages and perhaps sensitive (maybe even engine ECM) items down stream might complain by $ending $moke $ignals........
Given more then a few unknowns here, I'd be inclined to just take the dead duck totally out of circuit by disconnecting it's input from the stator and its output (typically batt. term start solenoid), then just temporarily run very light on the controllable loads (lights, radio, fans, disco ball, etc) running off the batt.....Would work with my motor anyway.
Your motor (I don't know yami's all that well) may draw a batt down faster then my old 1992 175HP carb'd motor, this being dependent on the various uncontrolled engine loads i.e., EFI's stuff, ECM, lectric fuel pump, etc......I suppose once out of circuit and running I'd be watching your dash volt meter as you ran, should stay 12V'ish for a good long run if its not drawing too much.
