Wiring of a 1980 Catalina 27

[Ajay73]

I want to look at my C27's wiring with an eye towards changes/upgrading. Is there an up-to-date wiring plan in the form of something like the attached link posted by maccauley123? I'm just starting to get familiar with the subject of sailboat wiring(I just bought the C27 this past August) and quite honestly some of the wiring diagrams I see are really confusing. I've got a book by Don Casey entitled "Sailboat Electrics Simplified" and it's not bad but the attached link from maccauley123 seems very clear to me, gives some sizes and other information and I believe can form the basis of understanding what I need to do. It's a little thin regarding the engine/alternator circuit but I can probably work through that. I don't plan on putting in a lot of sophisticated equipment/systems, just the basics that the boat came with from Catalina (running lights, cabin lights, knot meter, depth gauge, mast lights and of course engine circuits)but updated with more appropriate wire sizes, terminals, etc. I guess my feeling is that for someone who just wants the basic electrical system to be solid there should be an "off-the-shelf" wiring plan out there. Any help you can be will be greatly appreciated.

http://www.sailnet.com/forums/gear-m...lp-needed.html

[arf145]

I'll be happy for you if someone follows up my reply with a link to exactly what you want, but...I don't expect there is such a thing for you. And of course with a 30-yr-old boat most have diverged from the original. I found Nigel Calder's Electrical/Mechanical book to be a big help. Best you know the reason for the wire size needed for a particular run length and demand anyway.

[mitiempo]

The diagram by Maccauley123 (shown below) would not be a great one to follow. It is confusing, the bilge pump is after the main switch when it should have power when the switch is off, the negatives are not clearly defined, and I don't think his second switch is necessary.

As posted by arf above, I very much doubt your wiring is close to original after several decades. I virtually never ask for or look at an original schematic when working on a boat - they are seldom accurate.

[n8kraft]

If you have the original manual that came with the boat it has a simple drawing describing the original electrical layout. You can get more original manuals on the Catalina 27 website here: C27 Manuals

[btrayfors]

I agree with mitempo. In addition to what he said, the wiring size from the batteries and, especially, between the switch and the panel is too small, and the 100A fuses are too small since they're effectively in the starting circuit.

Better start anew.

It would also be good to decide whether you're planning to route all charging sources to the house battery bank and use some sort of automatic charging device (like an EchoCharge or DuoCharge or other) to maintain the start battery, since that decision impacts on much of the heavy DC wiring.

Bill

[mitiempo]

I think the best plan is to draw your own schematic. I'm guessing you will have a start battery and a house bank. Decide how they will be charged from the engine. Catalina and most other builders charged through the main (1/2/both/off) switch but that isn't a great plan for several reasons. The better way is to routs all charging, from any source, to the house bank and charge the start battery with an Echo Charge or ACR. The main switch becomes a control for use, not charging - easier to use and simpler. From the main switch output's common post there are feeds to the starter and to the fuse/breaker panel. The panel feed wire should be able to handle the entire panel's load with 3% voltage drop or less. From the panel the circuits - lights, electronics, etc - are branched off to each.

On a 27' boat 14 awg is probably a good choice for many circuits. For deciding on wire gauge this link AWG by wire length/amps calculator
will let you determine the gauge required. The distance is from the source to each load and back. I try for 3% drop or less for everything but lights can tolerate more. The wiring for nav lights and feed to the mast should be 12 awg but it is easy to figure out with the link above. Bilge pump wiring shouls be direct from the battery and not through the main switch. Fuse at the battery for this and fuse the main battery feeds as close to the batteries as possible - ABYC calls for 7" but that isn't always possible.

[Stu Jackson]

Here's one that should answer the basic engine/alternator wiring issues. The PP (previous post) shows the downstream DC wiring quite well. This link includes options as well as a very good wiring diagram from this message board.

Basic Battery Wiring Diagrams

The detailed wiring diagram came from this topic, in the Electrical section of this message board:

http://www.sailnet.com/forums/electr...dc-system.html

If you want sources for more boat electrical systems, try this:

Electrical Systems 101

[eherlihy]

The OP asks for the basics. Here they are;

1. Use the wiring size recommendations that Stu Jackson points toward.

2. Follow the ABYC Color code.

3. Make a working diagram.

Here is the ABYC Color Code (a lot of this stuff does not apply to a sailboat);


In addition, you ask for how to do the engine / alternator circuit.
Here is my current wiring diagram, for my basic charging circuit for my Universal M-25 with the Westerbeke Admiral's instrument panel on my Oday 35;

Not shown in the diagram is that I have an IOTA 30A Charger connected to the house battery.

You can see that in a few places I did not follow the ABYC color code. One example is the starting circuit, which uses a white wire with a red stripe on my boat. Part of the reason is that I could not find any marine grade tinned yellow wire with a red stripe, but instead I used the AWG10 White / Red that the previous owner paid big bucks to have installed by a pro.

Another example is that my negative conductors are a mix of yellow and black. This is because I am slowly changing out circuits, as needed, and as my budget allows. I am not doing a wholesale rip & replace (I would rather be sailing).

However, I have documented the color code that I have used, and that makes it acceptable per ABYC.

[Stu Jackson]

Nice diagram. Well done. For the OP: It does, however, if I read it correctly, use the 1-2-B switch as a charging source switch as well as a use switch (see my links above for recommendations for taking the AO to the house bank and NOT the C post on the switch), and does not show the distribution panel from the C post.

Good ideas for showing all the panel gauges and the wiring color codes.

[eherlihy]

Yep Stu, you are right. I am using the 1 B 2 switch to control charging and use.

I use the house bank ONLY (bank 2 a group 27 Trojan) to start, run, and power the DC systems when at anchor. The dedicated starting battery (a WM Starting Battery), is only there as a backup. By the way, my M25 starts fine with the 90A fuse.

I have thought of moving the wire from the C lug to the 2 lug of the battery switch, but the system that I have now is working, and, I have the upgraded Leece Neville 90 amp alternator, which also has a semi-smart regulator. If there is no load, it shuts off before the diodes pop.