Planning a Rewire

[gata119]

Hello Gentlemen,

Not sure if this belongs in the Electronics forum or not.  I am planning a rewire because my full rebuild hopes have been on hold for some time now.  Would you guys be so kind as to take a quick glance at the attached "amateur" wiring diagram?  I have been researching this enough to make me crazy.  I may be "off" on some of the wiring/cable sizes.  Please let me know what you guys think.

Blue Seas switch and ACR
Honda BF225
Group 24 batteries

Thanks!!!!!!!!!!!!

[RickK]

Nothing jumps out at me as wrong.  On my 230 Explorer I have a 75Amp breaker on each side of the ACR, maybe I couldn't find 100s? From the house battery to the helm I have a 30Amp CB.  I don't run much electronics so the draw is minimal.  I do have a windlass that I run off the starting battery and make sure I have the engine running when I use it.
I assume the batteries are in your console and that you are using 1ga to make the batteries "seem" like they are in the aft, where the studs are. Should be ok, depending on who you ask.  I am doing the same thing on my 170 rebuild but I am using 2/0 wire so there is no loss at all.  I am then going to 4ga from the studs to the engine so I can get the cables into the engine.  Do you know the draw on the batteries when cranking the engine, amp wise? The goal is to have little to no drop in voltage when cranking. I think my 250 is close to 200 amps when cranking.  My 90/115 will draw about 125-140 amps.  So the 2/0 is a little overkill on mine but the battery will "seem" like it is in the aft, 4 ft away from the engine instead of 12 ft forward in the console, and the starter will spin fast and turn the motor over, no problem.  I ran 2ga to the trolling motor up front - only about an 10 ft shot total but the trolling motors don't draw that much.

[gata119]

Sounds good.  Yes, I am relocating my batteries from aft to the console.  I have to extend the stock Honda cables another 13-15'.  Someone told me according to the Honda rigging manual, it suggests using 4ga. wire to extend cables up to 30'.  That shocked me that It suggested as small as 4ga. for a longer run, so I am using 1ga. just because.  The 250amp fuse should be able to protect the 1ga. wire.

Does anyone know if the 250 amp fuse to protect the starting cable has to be on that side of the switch or can I buy one of the cube terminal fuses that bolts to the starting battery stud?

Thanks!

[RickK]

Here is my power center in my 230.  I don't have a CB between the switch and the engine, in fact my Johnson on the little boat doesn't have one either.  Is the CB a Honda thing?


I just bought some new batteries for the 230 - Optima AGMs and the Guest charger I had on the board is no longer there.

[gata119]

The fuse between the switch and the motor is kind of a debate among the internet folks apparently.  Forgive me if I'm wrong on parts of this, but ABYC says that you need to protect positive wires with fuses and such (except for the starting cable).  That is a major paraphrase on my part.  Some people argue that you should anyway to be safe.  My boat currently does not have a fuse there either, but since I will be redoing it all, I figured "why not".  I guess it protects that long cable run to the motor if the cable becomes compromised at all.  If someone has anymore insight, please do tell.  I see that you placed circuit breakers between the ACR and the switches.  Why those instead of fuses?  I'm still learning.

Thanks!!!!

[RickK]

I see that you placed circuit breakers between the ACR and the switches.  Why those instead of fuses?  I'm still learning.

Thanks!!!!

The CBs are on the input of the house and the output to the engine.  The ACR senses voltage differences between the two voltage sources (batteries) and will connect the two sources for charging when the charging source (engine) is in place and the house battery needs charging.  They work great.

[Capt. Bob]

The fuse between the switch and the motor is kind of a debate among the internet folks apparently.  Forgive me if I'm wrong on parts of this, but ABYC says that you need to protect positive wires with fuses and such (except for the starting cable).  That is a major paraphrase on my part.  Some people argue that you should anyway to be safe.  My boat currently does not have a fuse there either, but since I will be redoing it all, I figured "why not".  I guess it protects that long cable run to the motor if the cable becomes compromised at all.  If someone has anymore insight, please do tell. 
Thanks!!!!

Indeed it is a debatable point. The main pro for a fused starting cable is in case of a dead short. This is most likely to occur where the cable (as you noted) becomes chaffed and shorts to ground, say on some metallic part of the craft (think engine room) resulting in fire. Chafing can occur in boats like ours but often that would be due to contact in a non-conductive (but not always) area. That would be my guess as to the logic of ABYC. Of course fire could also occur on the engine itself on an outboard so the reasoning for fusing can be justified. I don't recall anyone bringing this up before and like yourself, I have not fused my cable either.

You have been a Forum member for awhile so I'll assume you have read some of the exchanges on battery cable sizing and voltage drop. From everything I have ever read, no more than a 3% drop is what you are trying to obtain. The problem with that is the conductor size becomes huge (as does cost) to achieve that level. The "rule" that many follow is 4AWG if batteries are in the stern and 2AWG if under the console and any bigger is BS.

This is preached because it is how it was always done and it works. You can't logically argue with that rationale. The voltage drop in your case (assuming 200amps at the starter since we don't know the actual) using 1AWG would be 6.6 % at your post in the stern. Is this acceptable? Using the logic above, yes. To obtain a 3% max drop you would need to go to a 4/0 wire. So is the 3% something we as boaters need to adhere to? Who knows and pretty much apparently, who cares. You should be fine.

Personally I run 4/0 directly to the motor. It just fits under the old Yamaha and I keep a watchful eye on chafing in that area. It cranks without a thought, even on a battery not a full charge. Did I reach the 3% drop? No, more like 4.5% but it seems to work well, especially in keeping the batteries charged while underway with Yamaha's primitive system found on a 25 year old outboard.

Good luck.

[gata119]

Thanks for the info Capt. Bob.  You are correct, I did try and look at the charts to see what size cable I need for the length of run to accomplish the 3% max voltage drop.  That's when I figured these charts must be for the perfect world.  Like you said, it's probably because of the cost and space that most people don't follow what it actually recommends.  Thanks again, I definitely feel more confident now with this setup.  I may get rid of the fuse in the starting cable. 

[gata119]

I figured I would post the final product.  I hate when a thread has no closure.  I really enjoyed doing this project.  I learned a lot as well.  I replaced all the wiring, switch panel, fuse block, negative and positive bars, etc.  I also moved my batteries from under the splash well area in the back to under the seat in the console.  There are some things I think I would do differently next time to make everything look even tighter and cleaner.

1. I connected and started all the wires from pumps, lights, etc. and ran them back to the console.  It seems it would be easier to make everything in the console look really good if you connect all
    the wires in the console first and then run the wires out.
2. I guesstimated all the battery cable lengths and ordered them prior to installing the batteries, ACR, power bar, etc.  I ended up with cables that were slightly too long which made it difficult to
    make them look tight and clean with the extra length.  Next time I think I will try and make my own cables on site or measure and order them after the batteries, ACR and bars are installed.
3. Terminal Blocks:  I wasn't sure what these were used for.  I used one terminal block to combine all the nav. light wires into one wire.  That way only one wire was going to the switch for the lights
    I read later that some people will connect all the wires in the console to a terminal block and then run all the wires from outside the console back to that terminal block inside the console.  This
   seems like  it would make wiring everything and making it look really good a lot easier.  It would also probably be easier to replace wires if necessary.  What are your thoughts?

When I have someone rebuild the boat (still a dream at this point) I want to do all my own wiring again.  So, if you have any thoughts or suggestions, please let me know.  Especially about the use of terminal blocks.  Thanks!!!

[Capt. Bob]

 

[RickK]

Nice work.