twin engine 1 alt. 4 batterys 2 house 2 motor wiring diagram

[max2fastboat]

Hi all here the deal I have a 1987 Thompson daytona with twin 470's. she is set up with 4 batterys
2 house and 2 starts she only has one battery switch, look's like it had 2 switch at some time in her life.
Only one of the motors has a alternator. O and it has the original charger still.
Queston's
1. do you all think I need a second alternator?
2. does anyone have a diragram as to how this setup should be?
3. where should I start to trace the system I have out?
4. what would be the best wire setup, ie..islators, #of switches,second alternator and how to
wire it into the system?

Thanks for everybodes help

 

[max2fastboat]

Re: twin engine 1 alt. 4 batterys 2 house 2 motor wiring diagram

Yes the best merc ever built the 470 I was told and all so have checked that the starboard engi has no
alt on it the port engine has the after market install. I chased all old wires on the starboard engine but
never hurt, to do it right,do it twice. That being said what's the best config for a set up like this if a pro
was to set it up for your own boat? just looking to start a shopping list so when I pull her I can get right
in to her rewire which will be a total replacement of all the old wire and gauges. everytime I would take the
wife out another electrcal problem. And if mum's not happy nobody's happy (and the boat's on CL)

 

[Don S]

Re: twin engine 1 alt. 4 batterys 2 house 2 motor wiring diagram

1. In keeping with the OP wanting to keep costs down I selected a low cost NON-switching isolator. Basically nothing more than a high current rectifier that only allows current flow in one direction.

I'm using the same exact parts. Only I have the power from the alternator going to the isolator first. (This is also how Merc recommends hooking them up) This keeps the house and starting batteries charged at the same rate. In bubba's drawing, only the house batteries are getting charged through the isolator. If the house battery is full, it keeps getting charged as long as the house batteries are low.

2. With the Perko switch(s) in the OFF position all electrical power to the helm is turned off.

3. The house batteries are NOT shut off with the Perkos switches, that's what breaker panels are for. With that said, the run should still be fused at the battery to protect the wiring.

In this drawing, ALL power is shut off, not just to the engine. No need to turn off individual breakers (or pull fuses if you don't have breakers)
You can also shut off the starting batteries and use only the house batteries when at anchor or not needing engine power.

Each engine now has it's own switch in case something happens to one engine.

Both engines now charge both house batteries since both batteries are hooked together in parallel creating a single large battery.

You will also need two alternators. If you have only the single OEM charging system, it's not really big enough for charging 4 batteries.

 

[Don S]

Re: twin engine 1 alt. 4 batterys 2 house 2 motor wiring diagram

One thing I will caution about again is not having two alternators charging the same battery or bank of batteries.

Nothing wrong with that, and it happens all the time with twin engine boats.

http://www.perko.com/images/catalog/pdf/Fig 8501-8504 Inst (8500INS1).pdf