Stray current corrosion(?), hydraulic steering

[Skip Hood]

Hi folks -

Maybe this should post under the electrical topic, but then again, it relates to steering too. Mr. Moderator, please move if needed.

I installed Teleflex Seastar hydraulic steering on my 2002 CD-22 a couple years ago. My brother put the same model steering system on his Grady White about a year earlier. Both of us are already getting pitting on the cylinder shafts, causing the seals to leak. This seems awfully premature for what should be a highly corrosion-resistant part, especially since these boats are in kept inland, on trailers, and thoroughly de-salted between trips.

This is what Teleflex had to say: "What you and your brother are experiencing is called " STRAY CURRENT CORROSION ". This means there is voltage going into our shaft and causing this problem, also means that your boats bonding system is not up to snuff. You must inspect all grounds and ground straps and zincs. If you take a good multimeter set it at 12V put the boat in the water and put the red probe on our shaft and the black on different parts of the engine you should not get any voltage readings. Our cylinder grounds to your engine."

My brother did that test and confirmed there was indeed current flowing.

OK, but hmmm. Not really sure what my CD's "bonding system" is other than it has something to do with grounding. But I'm pretty sure the factory and dealer installed my wiring, engine, etc. according to the norms for boats of this type. No oddities apparent in anything else having to do with my boat's electricals. And the Teleflex steering was installed by the book, which mentioned nothing about special grounding. So if the explanation above were true, seems this would be a common issue for just about everyone with hydraulic steering systems. Never heard that was the case.

Anyone else come across this problem?

Thanks,
Skip

[Captains Cat]

I have and on the old boat had, a large ground wire running from the engine mounts to the battery negative lead. This is the "ground" on our boats, lacking a big plate in the bilges or outside the boat. This was installed by the engine outfitter. Better make sure you have one too.

Charlie

[thataway]

The large ground wire from the engine block to the battery is part of the 12 volt circuit. (Negative). If there were "grounding" of the hyraulic cylinder it would be directly connected to the engine, or some metal object connected to the engine.

On the Tom Cat 255, the ends of the rams are connected directly to the "Steering Tube" which is part of the engine bracket--should be grounded to the engine itself--and there is direct wiring to the bracket.

The ram is bolted directly to the "steering arm"--which should be directly connected to the engine block, and turns the entire engine assembly. So this should also be directly grounded.

I wonder if there is a different method of connection of the suspect ram and cylinders?

The ground system is several parts: lightning ground--if present should not interact with any other electrical circuits. Bonding ground--ties all metal below the water to the zinc--"the Green wire". 110 Volt ground circuit--(another Green wire--most boats like ours have a galvanic isolator and the ground floats). Finally Radio frequency ground, especially if you have SSB or Ham radio, is connected directly to a plate under water.

How much voltage is your brother seeing between the engine block and the cylinder?

The company seems to assume that this is related to stray current--and only when the boat is in the water. Since your boat is on a trailer, then this should not occur. (Ie if the boat next to you in the marina has been mis-wired, this will cause current in the water, and excess electrolysis on your boat. If a battery charger is mis connected, it can cause similar problems) But nether of these could be the case.

No I have not seen this.

[Larry H]

I think the Teleflex guy is trying to avoid a warranty/quality control problem.

Outboard motors have bonding wires connecting the block, leg, gearcase, and transom bracket together. As Bob said the steering cylinder is bolted to the transom bracket and steering arm of the motor, and so is grounded to the motor.

Stray current corrosion is only present if the boat is in the water in a marina and connected to the shore power. If the boat is in the water and the motor is tilted clear, the only part of the motor in the water is the bottom of the transom bracket and there is usually a zinc there.

If you take a digital multimeter, set the scale to ohms, and measure the resistance between various parts of the motor, you can find out if the parts are grounded to each other. The important thing is to see near zero resistance between the zinc and the motor block. You should also see near zero resistance between the steering rod and the negative battery terminal on the motor block. Switch off the battery prior to making resistance tests to protect the meter.

I cannot imagine how a trailer boat could have any significant corrosion on the steering cylinder rod caused by stray current corrosion.

Questions: Is the Grady White a sterndrive or outboard? Do you have shore power on your boat? Do you plug in in marinas? Do you run a battery charger while plugged in in a marina?

[Skip Hood]

Thanks, all -

I do plan to check for resistance - or lack thereof- between the various parts of the steering cylinder, through the steering arm, motor mount, down to the zincs, & so on. I presume if I find none that the Teleflex guy's whole theory on why this corrosion is happening is out the window. If I do find things in the ground path that should be electrically connected no longer are, then will do the in-water stray current check he suggests.

Meanwhile, to answer your questions: The Grady with this same problem is also a standard rigged outboard. No shore power, battery charger or anything that gets plugged in at marinas for either boat. I believe my bro measured about 5 volts possible "stray current" on his boat in the water, but wasn't there to see.

Thanks for the help so far.

[Larry H]

Skip,

I am very skeptical of this 'stray current'.

If a boat has no shore power connection, stray current would only affect metals in the water. Perhaps the SS prop and the aluminium gear case if the motor was down.

The Teleflex rep might have been referring to a stern drive or shaft drive motor, but I still think salt corrosion is the most likely. Having not seen the voltage test on the Grady White, I don't know what voltage was read, but 5 volts would be draining the battery fast and would indicate a short in the 12 volt system.

Digital multimeters can show random voltage reading, usually in the millivolt (.001volt) range. You can even measure a voltage created by squeezing the probes between your fingers, one in each hand!

[thataway]

Agree with Larry. Often voltage potential is measured using a silver chloride electrode when looking for galvanic corrosion. See: http://assets.fluke.com/appnotes/electricalpower/B0269b_u.pdf

The voltages usually found are less than a volt--and with very low current flow.

The galvanic corrosion is a different situation than stray current from a 110 volt AC system. There can be other causes, but they involve some damage to the boat (such as a lightning strike, loss of blocking diodes etc) or mis-wiring.

[computer-rooter]

I'm into my 3rd spring with Baystar hydraulic steering. My boat is docked in salt water year around and has an autopilot plumbed into it. It shows nothing like what you describe. It gets crud on the exposed part of the shaft, but that wipes right off. There's nothing special about my 22' classic's wiring, except perhaps that I redid it recently and I have a separate ground to the transom mount. I thought it might help the tilt servos. Maybe it's preventing the problem.