twin batteries on the twin I-4 boat


7

79Formula233

New member
Hi all, my 79 233 Cuddy has twin batteries outboard of each engine. There is an electrical switch 1,2,both,off back there also. When I start my boat I would like to use both batteries to start each engine, for added power in starting. When the "both" switch is selected, are both batteries engaged, or only the battery near each engine? I would like to add a third battery as a "house" battery, and run all the electrics off of it and save the two main batteries for starting the boat, only. I was thinking I could buy two new starting batteries and move one of the existing deep cycle batteries to the house position, then I could get more starting power with more amperage and make it highly unlikely that I will ever be stranded with a dead battery. I want my boat to be super reliable as I will be taking it out across the bar into the ocean, a dangerous trip to be sure out here in the Northwest. Thanks, Roy
 
Both batteries are engaged when switched to "Both" provided the switch is wired correctly.

If you want to use a deep cycle as a "house" battery for electronics, that's fine. For starting, I'd go with a regular lead-acid (I use Die-Hard Golds).
 
79 FORMULA,
ADDING BATTERIES IS GREAT, BUT THEY NEED TO BE CHARGED. YOU HAVE 2 ALTERNATORS AND THREE BATTERIES. THEIR MUST BE AN ISOLATOR INVOLVED, IF YOU WANT TO KEEP THEM SEPARATE. VERY DANGEROUS IF EQUIPMENT FAILS.
THE EASIEST METHOD IS TO HAVE ONE PORT BATTERY, JUST TO START THE PORT MOTOR. BELIEVE ME, YOU DO NOT NEED TWO BATTERIES TO START AN ENGINE. ONE IS SUFFICIENT. THIS BATTERY WILL BE CHARGED FROM THE PORT ALTERNATOR.
YOU CAN PARALLEL TWO GROUP 27 DEEP CYCLE BATTERIES AND USE THEM TO START THE STARBOARD ENGINE, AS WELL AS POWER THE HOUSE SYSTEM. THESE WILL BE CHARGED FROM THE STARBOARD ALTERNATOR, IF YOU FEEL YOU NEED TWO.
YOU CAN INSTALL A PARALLEL SWITCH THAT CONNECTS BOTH BATTERY BANKS TOGETHER IN AN EMERGENCY. THIS CAN BE ACCOMPLISHED WITH A MANUAL SWITCH OR AN AUTOMATIC SOLONOID WITH MOMENTARY SWITCH MOUNTED ON THE DASH.
THIS IS THE SAFEST METHOD. GOOD LUCK.
 
Will this work?: Three batteries, with two on one bank, one of the two being a deep cycle with its own 1,2,both,off switch and a battery isolator between the batteries. The second bank single starting battery with its own 1,2,both,off switch, with the 2 position jumpered from the deep cycle of the first bank? If this would work in theory I could have the power of three batteries available to start each engine! I want freakin overkill, I have no intentention of being stuck without power to start my engines out in the ocean. I'll have my little kids on board and don't want to take any chances.
 
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