Wiring a plate aluminium boat

[allanwh]

Hi,<br /> Would appreciate some advice on wiring. I have just built a 20 ft aluminium boat and had a honda 130 fitted. I have wired the boat apart from the motor myself and made sure ( on advice) that I did not ground the negative supply of the battery to the hull to prevent electrolosis. Having completed the wiring of lights, sounder, radios etc I checked and found the batteries were refernced to ground via the hull of the boat. I disconnected my wiring and found it is the motor wiring that is grounded to the hull. can anyone tell me if this is correct and give me some advice. I am also getting a lot of squelch on my radio when my sounder is on?? I would appreciate any help on this matter... Thankyou very much.. red skies at night and tight lines....

 

[DJ]

Re: Wiring a plate aluminium boat

whybee,<br /><br />The hull of your boat is NOT a suitable ground.<br /><br />Why any engine installer would ground anything to the hull is beyond me. EVERYTHING should be grounded back to the battery.<br /><br />You can correct this yourself or have the installer do it.<br /><br />This correction may help your noise problem.

 

[crab bait]

Re: Wiring a plate aluminium boat

djohns is sooo right on this...!!

 

[Skinnywater]

Re: Wiring a plate aluminium boat

Excellent!! Great, I've finally found what I've read before here but couldn't find again.<br /><br />Djohns or crab bait, one of you wrote this before 6-8 months back, your firm expression NOT to ground your aluminum hull.<br /><br />Now trust me that I'm only wanting to learn and I am concerned to wire correctly...not to debate or argue.<br /><br />I rigged everything except the motor and its remote. I grounded everything, lights, guages,accessories to the hull. After I did this I read your warning in that elusive previous post of yours NOT to do this! <br /><br />Now, here is my findings and reasoning. Remember, my boat dealer rigged my motor and battery.<br />My battery is remotely grounded to the motor. My motor is directly grounded to the hull. With my fluke, my ohms resistance from battery ground to motor ground is .001 ohm. My resistance from engine ground to hull is .002 ohm. The resistance from battery ground to hull is .002 ohm. These figures say my battery ground and engine ground are definately grounded to the hull and to one another. <br />Furthermore, my engine wireing is grounded to the engine block. Which is grounded to the engine transom mount. This makes sense because I have a massive zinc plate mounted on the transom mount of the motor(Honda). Armed with this investigation I relaxed my thoughts on a rewire.<br />Now my consern is elevated again because of your repeated warnings and seconded warning.<br /><br />Since I plan an occasional salt water experience, I don't want to have problems.<br /><br />Can and will you explain. Enlighten me and whybee please.<br /><br />I'm off to do a www search on the subject also.<br />And thanks for your warnings.

 

[allanwh]

Re: Wiring a plate aluminium boat

Hi,<br /> I too have been doing a little surfing on this subject and this is a confusing subject. It appears that the motor is bonded /grounded to the hull but as was pointed out all wiring should be run back to the battery negative and not through the hull even though as Skinnywater points out it is at the same potential. There are some good sites and forums on this subject but one I found very good for posting any problems is MarineElectrics.org<br /> and look in the forums.. Again thanks to all and I look forward to any further replies with interest..<br /><br />Red Skies at Night.......

 

[crab bait]

Re: Wiring a plate aluminium boat

since it's an alum. boat.. everythin' is gonna be connected to everthin' anyway.. <br />it can't be helped..<br />but you don't want to use the boat's hull as a conductor ( a path to ground )..

 

[Valv]

Re: Wiring a plate aluminium boat

Crab Bait is correct, don't use hull as conductor, run ground wires to grounding blocks from battery.<br /><br />Your motor is grounded to battery, but since it installed with metal bolts and clamps it will ground hull also.<br /><br />Interference with fishfinders, sonars, etc can be corrected wiring them directly to another battery.

 

[Skinnywater]

Re: Wiring a plate aluminium boat

HMM, I'm still confused.<br />O.K. Here please let me try again. My hull is grounded because my motor is grounded to the battery ground and is bolted directly to the hull.<br /><br />Now since my navigation light on the bow is mounted furthest from the battery, I'll use it as the example. <br />It has one 12v power wire to it. Its ground wire is 2 inches long and grounded at the base of the light. That 2" wire is the ground path, only because it's a load carrying wire. The ground is the same at that point as it is at the motor since it is solid welded aluminum plate. Since the entire boat is welded aluminum anything and everything aluminum is grounded (verified). The ground itself isn't a path, it's a ground.<br /><br />Please lay it on me. Again, I'm not trying to be a smart a$$ and I'm being sincere. I'm one **** of automobile diagnostician/technician/electrician. <br />However, I'm in training with things marine.<br /><br />My internet search only says it shouldn't be done.<br />Now I'm asking the experts why not? If it's unavoidable, like it appears, then maybe it's a non issue???<br /><br />Thanks again.

 

[Skinnywater]

Re: Wiring a plate aluminium boat

Further thoughts.<br />Ground path being the flow of electrons through the conductive aluminum hull from the nav. light to the battery, chemically interacting with salt water acting as an anode??<br /><br />Will the zinc plates surrender themselves before the aluminum hull??<br /><br />Seems like the aluminum hull will act like one giant ground buss bar.<br /><br />Friday nite CC and water wants to know.

 

[allanwh]

Re: Wiring a plate aluminium boat

Skinnywater,<br /> I am a licenced electricrian and have not wired many boats so that is why I posted the question as I was getting conflicting information. What you say is correct about the boat having the negative of the battery connected to the body of your motor and the body of the motor being connected to the hull therefore putting it at the same potential.. However no other wiring should use the hull as a return path (negative) to the battery. Cables should be run for this. If your nav lights are wired using the hull of your boat as a return that is wrong and has the potential for corrosion.<br />To clear the matter up look at marineelectrics.org and go to the message board. I posted this query there and the author of the site has replied in very easy to comprehend manner. What all posts here are saying are correct but the terminology we all use can be confusing... Anyway.. Thanks to all for their comments and experiences and sorry if I have caused some confusion.. Cheers...

 

[Skinnywater]

Re: Wiring a plate aluminium boat

Yes, the marine equation is the learning curve here.<br />I did a search for that site, I'll use a different search engine.<br /><br />Seems in our case anyhow our logical ground point would be a seperate ground cable to the motor from our consumers.

 

[allanwh]

Re: Wiring a plate aluminium boat

Skinnywater,<br /> The web address is www.marineelectrics.org so you shouldnt need to search for it. The author of the sites and author of various books is John Payne..<br />Best of Luck..

 

[ebbtide176]

Re: Wiring a plate aluminium boat

i believe the confusion is in the corrosion, not the potential. from what i've learned(here) the goal is to not have any electrical units relying on the frame ground, but to go directly to the battery via separate wiring. you would want to avoid any potential. and so also no attraction to the hull for corrosion. in other word, if there is a potential, confine it to the length of wiring, enclosed in insulation, not to the exposed connections on the frame/hull of the boat.