Logo
FULL SITE MENU

stray current

J

Justy

New member
Hi there I think I have a stray current issue with my aluminium boat- I was given and OHMS test from the manufacturer which involves disconnecting the negative battery terminal cable (to engine) and turning of battery isolator switch - then test from negative terminal to a clean screw going into the hull - manufacturer says reading should be OL (open loop) mine comes back at 0.04 OHMS. Anyway I think I have found the circuit leaking current it is the power tilt circuit. MY Question is this. Will the negative earth off the relay switch circuit always have current going through it when the ignition is on or only when the relay is acitvated via the switch on the remote? What I am thinking is that there is an issue with the earth on the power trim/tilt circuit causing current to find its way into the hull and lower unit of my outboard (is showing signs of pitting)
 
To answwr your question about current flowing when the switch is in the.OFF position, NO....
...UNLESS... the switch is defective in some way.

Switches CAN break internally and allow unintentional current flow. They can also "stick" on or partially on.

A boat can act like a battery part in the water. Aluminum is not only VERY conductive but is also weak at resisting giving up it's electrons. Especially if near a very strong or "NOBLE" metal like bronze or stainless steel (think propellers).

Even being docked near an unprotected/painted steel hulled vessel at a marina will cause galvanic corrosion as the steel acts as the carhode and the aluminum becomes the anode. The water they both rest in acts as an "ELECTROLYTE"...JUST LIKE...
...a wet cell storage battery.

The trick to protecting the aluminum hull is usually to offer the electrolyte a weaker metal, like ZINC or magnesium, to pull electrons from.

Boaters should use zinc anodes on their boats and keep then clean and "fresh". Especially in salt water.

Another thing boaters tend to overlook are the electrical "bonding" wires on things attached to the boat, like outboards, that are in the water alot.

You didn't say if you had an outboard but as an example, check out the link below for a Honda 90.
Item 9 is a bonding wire. Note that the wire depiction shows only ON⁷E attachment screw (item 31)...quantity required 1.
But the other end of the wire has an eyelet for attachment too.


Now see item 1, anode (zinc) in the link below and item 27, bolt. That wire end inside the dotted square is the other end of the wire 9 in the link above. Also note that the quantity required for item 27, bolt, is 2 because that's how the zinc bar, item 1 is secured.


If it's not already obvious, that zinc bar is the weak, sacrificial metal intended to "give up" it's electrons so that the other metals will live. The bonding wire is the electrical connection to help ensure the other nearby components are protected too.

This info may not be the solution to your problem but I felt that it's pertinant to boating and is important enough that owners be aware of the possibilities.

Good luck.
 
Back
Top