TOPIC: radio question

im wanting to put a simple radio with four speaker on my boat. my question is will my 74 40hp evinrude keep the battery up enough. im not fimilar with the charging system. im guessing its similar to a lawnmower?

thanks
Will

I'm not sure the amp output of your charging system, an owners manual should list this info. An AM-FM radio draws less than 5 amps and a marine battery can run one for days. If you add up you amp draw for what is in use you can calculate how long your battery would last from a full charge. If your amp draw is less than the what is being generated by the motor...alls cool. Starting the motor is the biggest draw of power from the battery. The faster your motor starts the less time will be needed to re-gain full charge.

A good read
www.thefishingline.com/marine.htm

Pretty sure you'd have a 5amp alternator but not positive. If you happen to read Italian there is an online catalog for Evinrude here.
www.old-omc.de/start.html