While trying to determine whether I had an electrical problem or a battery problem I spoke with customer service at MC. The told me up to 50 milliamps is considered normal draw when the boat is not in use. The ECM for the motor, radio memory and the computer for the gauges (MMDC black box I think) all have a slight draw.
After new fat sacs to replace my rear hard tanks a battery tender will be my next addition.
If you MC owners are interested in your gauge setup and computer then look at this link.
http://www.bwinstruments.com/Marine%20Product%20Group%20Menu.htm They are the OEM supplier to MC.