I think that might be difficult to say. Among other things,
it will depend on the actual capacity of your battery
(likely to be less than when it was new) and the starting
requirements of your inboard. Other factors that might
influence the minimum starting voltage are engine and
battery temperatures. Worst case is cold battery and cold
engine.

You can certainly experiment (when you have access to a
battery charger) to determine the critical voltage, but
expect it to change. Prudence will doubtless require a
generous margin of safety in any case.

You could be much better off with a second "starting"
battery and isolator.

Good luck.

Chuck

Mvd wrote:
Hi,

I am planning to make a device that gives a signal (beep) when my
voltage drops at a level that i cant start my boat engine. I have to
know aproximaly what voltage is the minium to start.

I have an 4.3l V6 mercruiser inboard. What will be a save voltage to
program in the device?