electric problem

[correllcr]

i have a 1973 apollo jet boat whith a 1979 mazda 13 b rotary engine i had an aluminum motor box built for it whene i took it out for the first time the motor box started arching to me then my fishing pole started shocking me and i trew it to the front of the boat and it was still shocking everything then anything metal started arching to each other and everybody was geting shocked there was so much electricity you could hear it huming i was told it probebly had a bad ground but it never happened whene i would run it in my driveway and i checked the ground the battery is grounded to the block the only other thing i can think of is the alternator is at the top of the engine about 4 inches from the motor box could this be causing it if so what should i insulate the box with any ideas help thank you

Mr
12 VDC cant arc across 4 inches, cant even arc across 1mm,
Do you have a multimeter? if not go down to walmarts and get a 10 dollar one
No need to insulate the box UNLESS you wish to sound deaden
Can you see burning on the alloy? Sure it was not a lightening hit) or the good lord chucking one at you?

[dragonjbynight]

I am going to have to agree with Jack on this one, no way is twelve volts sparking or humming along the whole boat. The only possiblility I could imagine is that your engine is electric start and your starter solenoid is somehow constantly on and grounded out; however, its a very remote possibility.

[CDK]

I've read this post several times, but it doesn't make sense.
Probably it were aliens dancing around the rotary engine!

[dragonjbynight]

Gremlins!

[PAR]

The only possibility I can see is the ignition coil high tension lead, but you be getting a huge hit and you'd likely try to jump out of the boat, before it knocks the fillings out of your teeth.

Take it to a qualified shop and have it looked over, as this isn't a usual issue and needs immediate attention.

[masalai]

Why is the 12 volt system EARTHED... FFS the negative has what is usually called a common rail, but NOT earthed, it is DC and is better "floating" - not connected to anything else... (If it is effectively earthed to the water, a circuit can be set up with some of the ignition coils via its earthing or fault making a circuit via the seawater which if so WILL cause you GRIEF with electrolysis and heavy corrosion of some submerged or salty-wet parts...

I am not an electrician and figured some tradie would have answered by this. I dabble in electronics and have wired 240v ac houses and mobile 12v & 24v DC vehicles in remote islands of Melanesia... as well as Certified to work on 33kv supply lines in Western Australia. so I am not an authority, just done a bit safely...

[alan white]

I'll guess you had shore power around for working on the boat and somehow it got involved with the aluminum box. The noise, a hum, would not be heard from a coil discharge (20k volts or more). More like a snapping sound.
Low voltage will hum (lots of amperage and low voltage), but you won't usually get shocked, and as said, arcing is out of the question.
As PAR said, especially if you are convinced no shore power was involved, stand back and have a pro look at it. That problem could kill you.

Alan

But then you said it was while out on the water running the boat. The coil must be involved. A crack in the distributor cap or the coil itself could bleed high voltage to some metal part that's not bonded to the engine. Make sure all metal parts (brackets, frames, etc.) in the engine area are grounded to each other

[Ike]

As many have said here low voltage (12v dc) would not cause this kind of arcing and snapping. This sounds like a high voltage ignition wiring problem. Go through the igntion system. Check the wires from the distributer to the spark plugs. Make sure all of the caps and boots on these wires are in good condition and firmly in place. In fact I would probably put all new ignition wiring in making sure you buy ignition wiring for marine use (yes there is a difference. It is a different SAE standard) I suspect that somehow the aluminum cover is making contact with the ignition wiring. If the wiring insulation is old and cracked or just not insulating any more it will arc over to the aluminum engine cover. Make sure the cover doesn't touch any of the ignition components, wiring, distributor, coil, etc.

[correllcr]

thank everyone for your advice i replaced the igniton wires and rerouted them a little bit so they weren't toching the motor box and took it to the lake and it worked

[masalai]

Hooray, one happy boater...

[mooseye]

I am amazed that you did not abandon ship with that much juice jumping around. A spark from a plug wire is a nasty jolt.
Glad you solved it.
My first thought was a faulty voltage reg or diode in your alternator, but oh well.