+12V output from MCM harness/Fused ACC panel

[Jerryh3]

Trying to add a second battery to my boat and have a question. The current Accessory fuse panel seems to be connected to a RED/PURPLE wire coming off the harness on the back of the engine. My plan is to separate all house loads and transfer them to a "house" battery. So, I traced this connection as well as I could and it seems like it is a direct connection. So, the plan is to just cut this connection and splice in a 4AWG wire directly(with fuse) to the house battery. Just wondering if anyone knows if this RED/PURPLE wire from the harness has any other function or sees anything wrong with the plan.

 

[Don S]

Re: +12V output from MCM harness/Fused ACC panel

The red/purple wire is supposed to go to the B terminal on your ignition switch. Sounds like it's now going to the fuse panel and and a fused wire goes to the switch from the panel.

Then your new wire goes to the fuse panel for house power.

 

[Jerryh3]

Re: +12V output from MCM harness/Fused ACC panel

Thought so. Just looked a little odd. The current battery had a 2GA for the starter and a 4/6ish GA wire that I always assumed went to the fuse panel. As I dug into it yesterday I discovered that this wire actually went to the tilt/trim motor. So, I was like, Ok where's the run for the fuse panel? The RED/PUR was spliced to a 4GA wire running up to the fuse panel. I went to the schematic book and saw that RED/PUR is usually run to the ignition switch and had a note that "Up to a 40A fused load" could be also connected, but I just wanted to make sure. I'll try to find the ignition circuit on the panel and identify it. So, summary... Battery 1(24 Dual purpose) will only be connected to the starter, and battery 2(31 Deep) will run everything else. A Battcom combiner is used to connect the two.

 

[Don S]

Re: +12V output from MCM harness/Fused ACC panel

Here is a thread on the combiner/VSR or some of the other names for them.

http://forums.iboats.com/showthread.php?t=513954

 

[Don S]

Re: +12V output from MCM harness/Fused ACC panel

Here is a typical inst panel wiring diagram for Merc.

View attachment #23 GM BB V8 GenVI 98-01 429.pdf

 

[Jerryh3]

Re: +12V output from MCM harness/Fused ACC panel

Here is a typical inst panel wiring diagram for Merc.

I saw this one after I started working on it. The engine manual doesn't have the instrumentation harness info. Anyway, it's all done. Just have to wait till the spring to see if it works.