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Random Quote: Numb it with ice first idiot...then snatch it out..... it will bleed a little bit
I have a Pursuit 3100 with 6.0L Crusaders. The alternator on the starboard engine went out a few days ago. I would like to use the boat this weekend. My question is this: Is it O.K. to use the alternator on the port engine to charge both batteries while running (I can set the battery switcthes up to do this). I am not sure, but I don't think it will do any harm to the port engine alternator although it may be putting an extra load on that alternator. However I would like to hear from someone who is a lot smarter than me on this subject.
I've got a single merc 350 thats been charging two batteries no problem for three years maybe 4
ditto, before I changed my starter a few years ago, it cranked better in the both position so I guess I got used to leaving it there. No problem at all.
Been charging 5 batterys for 8 years on one alternator, a 75 amp. No problem for a daytripper, not much & only short DC draw while engine is off. More of a concern if overnighting & batterys have been drawn upon heavily. Alternator will have to work longer & harder to restore full charge to batterys.
Sorry, meant Yandina. Both batteries receive chargewhen engine is running and when battery one or two is selected on Perko 3 way switch. When you shut down, 2nd battery is automatically disconnected leaving you with a fully charged second battery. The next time out I start on battery 2.
__________________ Tom Pass
Sea Blues II
'03 Key West 23WA
Honda 225
Little River, SC/Hamilton, NJ
Proud Parent of a Marine
I assume that these Crusader engines are EFI and you go offshore and you could be 45 miles out.
Now consider this ; how long do you think it will run on just battery power if the one remaining alternator dies?? 2 Ecms,2 Elec fuel pumps,plus other electrical load.
I will tell you my son's 6.0L 2003 Chev truck ran for 25-30 minutes after the Alternator died.
Replace the bad alternator and have two good ones. When will your present old overworked alternator take a crap.
Why install a combiner when you already have the battery switch in place? Put your $75.00 towards your new alternator.
Because a combiner only combines for charging. I personally cant easily get to my battery switch and dont want to have to worry about turning back and forth all the time.
Leave the switch in "both" too long and run them both down you wont be starting the engine and going home. A big reason for having two batteries is the safety of having a standby.
It also protects your electronics during startup. The engine draws from one battery and the elctronics from the other. With the switch, the electronics are alwasy seeing the power fluctuations caused by starting the engine.
Charging Both Batteries from One Alternator 
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