Croozin2

What alternators come stock on the 575 SCi? Does Merc still use the little Mando units? A buddy of mine has 575's and he installed the Optima blue top marine batteries. The batteries never seem like they have a full charge. Well, last night I was reading through my Jeg's catalog and it states that these batteries need a MINIMUM charge voltage of 13.8 and a max of 15 volts. A stock alternator usually puts out around 13.8 max since a standard 12 volt battery will begin to boil and sulfate at anything much over 14. Anyone else running this combo that might be able to shed some light?

JaayTeee

My 575SCi merc manual states
voltage output at: 13.9-14.7 volts.

I have blue top optima's, haven't had any issues,
other than stupidity, ( leaving things on after it's put away)
with mine

BadDog

If it is a Mando the voltage regulator is attached to the alt in a bell shaped container. Remove it and run some jumper to it so you can get at it with the engine running. Fully charge the batteries and let stand overnight. Reconnect and check battery voltage with a DVM and engine running.

The regulator has a potentiometer in it that can be adjusted. Crank it up until the DVM reads 14.whatever. Let it idle for a bit and recheck. Might be a good idea to check all grounds and clean cables ends prior to this. Sometimes the battery switch corrodes and eats some power.

Croozin2

Thanks BD, that's good info. When my Mandos took a dump some years back, the parts to repair were going to be almost as much as replacing with a Delco unit that put out twice the amperage (55 amps vs. 100 amps) so you can guess what I did. On my buddies boat I've never seen the voltmeters past 13.5 while running and it seems like once the engines drop back to idle the voltage falls off to just over battery voltage (according to the volt meters on board). The boat did spend some time in salt water so checking all the connections is definitely on the to-do list also.