Aluminum Boat Corrosion?

[Bassmastergm]

In order to check if there is current going to the hull of an aluminum boat say a bad ground for example. Would you check this by disconnecting the ground strap from the battery then hooking up a volt meter to the positive post then to the aluminum hull or would you still leave the ground connected? The reason I ask is that if I leave the ground connected to the battery I show 15 volts is this right the grond is connected to the motor then the motor is connected to the hull. But if the ground is disconnected I show nothing which is right.

[Burksee]

Either way, but use a 12v test light to check voltage drop.

In either case by connecting the test light/volt meter to the hull and touching it to the positive side of the battery, if the motor is properly insulated it should not light up/show any voltage.

[ESOX]

I am completely lost as to the question or the answer.:confused:

[Burksee]

Esox,

Its a bad idea to have the hull of your boat as a ground, it can cause corrosion and pitting. Its best to have the electrical system isolated/insulated from the hull. Meaning all lights and other electrical equipment should have two wires running to it. In some cases I've seen were the motor mounts will "ground" to the hull and cause the entire hull become grounded. You dont want that. I was trying to explain an easy way to check and see if your hull is grounded or not.

Hope this clears up your question. ;)

[ESOX]

http://www.michigan-sportsman.com/forum/showthread.php?s=&threadid=40158

If you were to take a test light/ meter whatever and hook it to the positive side of the battery and and the hull, it will show amperage weather the boat were properly wired or not.

[Burksee]

Not if the ground is properly insulated, If it is it would not light/show any voltage, much like an open circuit.

[Jason Adam]

Burksee is right. If the motor and ground circuit are completely isolated from the hull, you will not have a closed circut when you test from the positive lead of the batery to the hull. I don't know if this is the way aluminum boats are setup(as you could not use any screws or brackets touching the hull as grounding points), but regardless, he is correct...

[ESOX]

UH, aluminum is an excellent conductor. If you run a test between the Positive terminal to the aluminum hull, it will be grounded thru the ALUMINUM hull. Weather or not the wiring system is properly grounded to the battery.

[Getaway]

Esox,
The only way you could complete the circuit is if there were a ground strap from the negative terminal on the battery to the aluminum hull. Then, your test light would go "on" if you touched the positive side of the battery and the ground wire was on the hull of the boat.

On automobiles, there is a ground strap from the battery to the engine which makes chassis grounding possible.

[Jason Adam]

Bob is right. The battery needs to connect somehow to its own negative, not just a "ground" to complete the circuit.. If the negative post on said battery is not physically connected to the hull, a hull to positive terminal will not be a closed circuit.

[Burksee]

I'm assuming from the original post by Bassmastergm that he is trying to figure out if his hull is "grounded", meaning its somehow connected to the negative/ground side of the battery and/or cable.

Its always been my understanding that with anything aluminum that’s not what you want, you want to make sure "all" (Positive & Negative) circuits are insulated/isolated. They should be dedicated circuits, We use the term "hard wired", meaning both the positive and negative leads run direct from the feed/source to the load with out making contact/continuity to other object, feed or circuit.

If the hull was grounded it would become part of the "negative/ground" circuit from the battery. If its not you have an incomplete feed to ground, an open circuit. An open circuit in this case would be a good thing!

[MadCatter]

you are going to be grounded through your hull it is normal ... your negative post on your battery or batteries is going to have continuity through your hull .... almost all of your electronics are going to be hard wired though .. not because of corrosion, but to cut down on electrical interference. On your motor you have what is called a sacrifical zinc anode .. it is most commonly the trim fin on your motor or sterndrive .. It is designed to be attacked by corrosion before your hull is .. That is why you don't paint them and replace them if they start to corrode. When you turn your key on you are completing a circut so you will show voltage between your positive and your ground .. If your voltage meter has a continuity test on it .. set it to that and you will see that you have flow between the neg side of your battery to the boat hull ... Unless your motor is running you should only show a voltage of 12.7 volts or so ... 15 is about right with the motor running