Rewire of twin inboards

Discussion in 'OnBoard Electronics & Controls' started by Joe Cruise, Sep 13, 2024.

  1. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    Hello everyone,
    I've got a 1973 40' Cruise-a-Home houseboat, it has twin OMC 5,7 inboards, when I first got the boat the wiring was a complete rats nest. Every bit of it. To the point it didn't run .
    Well since then I've come along way, at first just to get the boat running I just pieced the wiring back together little by little. Until I knew the boat was operational before putting more time and money into it.
    After getting ready to install this new charging system I figured now is the best time to completely rewire the engine room and the engine harnesses back to the lower helm.
    So recently I started my rewire in the engine room. With 2 new charging systems each engine got new 1 wire alternators that will charge there own group 31 agm starting battery's. Then I got 2 Victron Orion XS 50 DC to DC chargers that will each charge a lifepo4 house bank from the starting batteries. So I gutted all the old wiring in the engine room . Hacked it all out . Down to the two engine wiring harness stubs. going back to the helm and one pos+ 6awg and 1 neg- 6AWG. That also went to the helm. I've also got the wiring diagrams from the boats website. So here's where I'm asking for advice. .
    I'm planning on buying all new marine grade wire and building 2 new harnesses that will wire to terminal strips under the helm. And go about 30' to the engines in the engine room. I don't think I'll put terminal strips in the engine room I'll probley just take each wire to it's final destination. Each engines wiring harness includes pos+ and neg-. 10AWG. Plus there's also the positive and negative 6gage wires that go from the engine room to the fuse panel under the helm . This panel was house and engine related fusing originally.
    Ok back to my question. In an effort to keep each engines wiring to itself should I put 2 new fuse panels at the end of the helm side wire harnesses. ? One port side engine and one starboard side engine fusing? As opposed to having only 1 fuse panel under the helm that would have to be powered by one of the start battery's. Which would mean that one of the engines battery would be supplying the voltage for both engines ignition and start circuits. Which id rather not have it that way . Right?
    Then if have a third fusing panel that will be fed off the house lifepo4 bank . Is that the correct way to wire the engines each having there own fuse box? So they each could supply and ultimately be responsible for there own circuits.
    Thanks for your help . I appreciate your time.
     
  2. philSweet
    Joined: May 2008
    Posts: 2,812
    Likes: 561, Points: 113, Legacy Rep: 1082
    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    You need to wire it like it is shown in the ABYC schematics. They do permit a non-crossover system, but I would not do that on a house boat. That provision is really there for outboards. Thus you need the negative engine tie per E-9.4.e. and the ignition panel can see both start batteries through to crossover switch. When you choose to close the crossover switch is up to you. It often depends on the float charging situation.

    https://law.resource.org/pub/us/cfr/ibr/001/abyc.E-09.1990.pdf
     
  3. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    I didn't realize i was required to wire it per anybody's schematics. I guess I'd have to see exactly what it is you're talking about. But my question is more towards whether or not I should put in two fuse panels one for each engine under the helm as opposed to the way it was wired originally which was the house and both engines were on one fuse panel .
    If you're referring to the crossover being the set of engines on off switches I mean I could do that I mean that's not a problem that could be you know done at any point but yeah I was just more or less talking about the whole each engine harness would get its own fuse panel under the helm and then wire according to that so they each engine had its own ignition and and everything was just kept separate the house and both engines port and starboard.
     
  4. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    Oh and I will have the negatives tied into the engine blocks and then ultimately once I get to that stage all negatives will also tie into the bonding system and AC grounds .
     
  5. fallguy
    Joined: Dec 2016
    Posts: 8,043
    Likes: 1,823, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Boat Builder

    Make sure and read the linked pages as instructed for Section E-9.4 (d) and (e).

    The crossover cable needs to be designed based on current draw and distance of cable and will probably be pretty big. On twin outboards like mine, the system is optional, but mine uses a BlueSea ACR amd associated cabling to connect the engines. I’m not sure I fused the ACR connection at the moment; probably not, because in my head I considered it starting circuit, but when closed; it could be pulling lots of current, I may rethink or double check what I did now!

    As for your fuse panel question, I personally prefer more discrete systems. For example, the starboard engine won’t crank, checking the fuses on the starboard fuse panel is just nicer than sorting and checking the wrong one by mistake. But it is a preference only.

    Each conductor on a DC system is supposed to be fused, so the total number of fuses is the same in all cases.

    Fusing the starting cable is not required on outboards.

    Just to add, the Bluesea fuse panels are really affordable, so I have 8 small DC panels on my boat, one for each starting engine and two for DC 24 hour circuits, and I run Czone for the main house distribution and 4 small auxiliaries.

    If it were me, I’d use at least 5 panels on your boat. One for each starter, for example, my Orions are fused and powered there, as convenience only to avoid long runs; starters need to be almost nothing, but my remote ACR, and Glendinning actuators run there. I’d run a fuse panel for anything that is always on. This way the House can be turned off an on as desired, but those panels stay hot. Mine have propane detection and a few other full time items like CO detection, refridge, etc. I actually had a small panel and had to add one; the remote battery switches are also fused there. Then each engine, and the house; guess that is 6.

    The downside to lotsa panels is remembering what is where and for that you ought to make an electrical book for the boat. It’ll help you more than you know in 3 years when something breaks.
     
    Last edited: Sep 14, 2024
  6. BlueBell
    Joined: May 2017
    Posts: 2,962
    Likes: 1,102, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    Hey neighbour!

    You ask leading questions.
    Were I in your shoes, I'd review the original wiring set-up.
    Was it successful or problematic?
    Are there reports of problems or did it work well.
    Someone designed the original system.
    If it has good reviews without any problems
    then simply rewire according to the original schematics.
    Simple.
     
    Tomsboatshed likes this.
  7. rangebowdrie
    Joined: Nov 2009
    Posts: 312
    Likes: 133, Points: 43, Legacy Rep: 10
    Location: Oregon

    rangebowdrie Senior Member

    Just a thought that may pay-off in the future.
    I did a job similar to what you're doing a few years ago for a client.
    I made-up the engine harnesses, terminating them at terminal strips mounted close to the engines.
    Wired the gages similarly, terminal strips close behind the gage panel with enough slack to allow the panel to be lifted out of its enclosure.
    My method allowed the gage panel to be pre-wired on the bench with an appearance similar to an aircraft panel, not like a "spaghetti factory".
    Then there was a main harness that just connected the terminal strips at the engines with the terminal strips at the panel.
    This allowed changes in gages/panel wiring/engine wiring/engine removal, without having to disturb the main runs.
    Also in the main runs were an extra ground wire and an extra hot wire.
    Take your time, keep things neat, don't run wires "hodge-podge" and draped over engine components.
     
  8. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    When I bought the boat it wasn't running and the previous owner that sold the boat to me hadn't ever had it running and didn't know it it would. All the wiring no matter where you looked. Was a complete disaster. Mostly unhooked and in knots or cut . Looked like a psycho ex sabotage kinda thing. Well I took a chance cause it was a pretty good price.
    So before I put any more time or money I to it I wanted to make sure both engines ran. So I basically pieced the wiring back together best I could in order to check the engines . And I was successful. They both run very nice. So I began rebuilding and remodeling the boat. Most recently I bought all new parts for the charging system , 2 alternators, 2 Victron Orion xs DC to DC chargers. Couple hundred feet of 4awg , mega fuses ,battery lugs and enough 4/0 to complete the charging system. But I figured no better to e than the present to get rid of the fire hazard rats nest in the engine room. So I cut it all out . All of it except the two harness stubs and a couple 6 gauge + and- that used to power the single panel under then helm. I've got all the original 1973 wiring diagrams. Not that they will serve as a plan to go by but they will help tell me what's what. But it made sence to me to include replacement of the two engine harnesses at the same time as I rewire the charging system. The way that will be set up is each alternator will charge its own Agm group 31 starting battery and the DC to DC chargers will then let the starting battery's charge the house bank. Right now that is 3 H8 lead acid 250ah battery's. Soon to be replaced with a 640ah lifepo4 . The house bank will then power the new DC breaker /panel and each engine will have its own fuse box located under the helm. Or at least I'm thinking that would be a good layout. Looking for advice or words of wisdom on the plan as it is now. I'll upload a picture of the two harnesses the way they were in 73. And I'd be copying that except putting the fuse panels on the helm side of them and changing the wire colors to the current ABYC color codes. As well as enlarging the current carrying wires to ABYC standards as well.
     

    Attached Files:

  9. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    Oh and as for the ABYC E9.4.e parallel connections. They way that sounds to me is that. On boats that have a parallel system. You would be required to make sure all it's components are of the same standard as the engines normal starting circuits.. it doesn't say that every boat with two engines has to have a parallel circuit installed. Just that IF your twin engines boat is or does have one. It needs to be installed in an appropriate way. Meeting the standards of what the engine needs and is required.
     
  10. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    The original wiring was done in 1973. Not only has technology advanced leaps and bounds since then( 51 years. )
    Id be a fool to just copy the plans as they are now. I don't even think there was ABYC in 1973 was there? I will be rewiring it in such a way that i can take advantage of the current technologies as well as updating it all to the current standards. I mean as long as I'm spending all this money I may as well build something that is enjoyable or something to help it hold some resale value to others.
     
  11. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    I think I'd much rather have just one well layed out breaker/switch panel for everything house related and 1 per engine. And leave all the confusion of so many panels out of the equation all together. Not to mention the need to write a instruction manual to help remind me where things are located. That don't seem like a very good idea to me.
     
  12. BlueBell
    Joined: May 2017
    Posts: 2,962
    Likes: 1,102, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    Really? Doesn't seem so much.

    Best of luck with your project Joe C.
     

  13. Joe Cruise
    Joined: May 2022
    Posts: 10
    Likes: 0, Points: 1
    Location: Tacoma, Washington

    Joe Cruise Junior Member

    Thank you very much. Appreciate the input
     
Loading...
Similar Threads
  1. tWEEka
    Replies:
    9
    Views:
    2,928
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.