Steer Clear of Electrolysis

Conduct a simple check to avoid a costly, corrosive problem.

By Fritz Grell
Originally published in the March 2008 print edition.

Electrolysis is the ultimate gremlin on a saltwater boat, corroding metals and leaving few clues to its source. Here, corrosion of steering ram was solved by replacing part and adding improvised ground wire, top.

Unless you know its former owner quite well and the boat’s history, buying a used boat can feel like a trip into troubled waters. But the truth is, whether you buy a brand new or used craft, you need to keep a close eye on all its systems on the first outings to catch any previously unseen glitches or kinks.

A couple years back, I bought a used center console with about 300 hours on the F150 Yamaha. I took the rig into Sailfish Marine Services in Stuart for scheduled service. The mechanic noticed pitting on the shaft of the hydraulic steering cylinder. The bottom of the hydraulic steering cylinder was wet with fluid, but the leak had gone unnoticed because the boat was cleaned often; that meant I had a problem. It was one on me, too. For the first time, I failed to notice signs of trouble because a boat was too clean.

We both assumed salt water had caused the corrosion, and considering the rig’s age, we contacted the builder to see if I could get a new cylinder under warranty. Sailfish referred me to Ken Little of Teleflex. Ken was quick to identify the problem as electrolysis, and agreed to replace the cylinder if the problem with the current flow was corrected.

The situation was this: The boat was stored wet in a slip, the engine always turned to one side so that the power knob on the steering wheel could be fitted under the console cover. This placed half the cylinder shaft under the cover. The curious thing was that the section under the cover was corroded, while the exposed portion was fine.

I contacted marine electrician Pete Demarsh and along with Sailfish Marine’s advice, Pete went to work to diagnose the problem. He tested for electricity flow in the steering system with the battery switch off.

The voltmeter was set at 12 volts, with the red probe in contact with the end of the steering shaft and the black probe in contact with various parts of the engine. The meter showed current flow in a number of areas where none should be present. Immediately, we suspected that an ongoing state of electrolysis had done its damage to the craft. Electrolysis is the flow of current between metals of different types in a conducting medium—such as salt water. Basically, the varying metal parts of your engine and boat create a weak battery, and the flow of current may gradually eat away the parts. The use of sacrificial zinc anodes normally takes care of this accidental flow, but if the flow is too strong, perhaps resulting from escaping current from the boat’s battery or from AC power at the dock, then the anodes are quickly eaten away and the critical portions of your engine can come under attack.

We checked all the grounding connections. All were clean and bright, and ground straps and zincs were okay. So we had a mystery. I decided to conduct a little experiment.

I made an 8-gauge ground wire with heat shrink covers on the connectors. I connected one end to the steering shaft between the lock nut and the washer, and the other end to an above-the-waterline motor mount bolt. Retesting with the voltmeter, we now found no current flowing, period. Problem solved. Where the flow was coming from, we still didn’t know, but we had the problem solved with a work-around. Perhaps I’ll eventually find the leak sometime down the road, but for the present I’ve gotten rid of the electrolysis issue.

When the new cylinder is installed, I’ll run the ground to the new ram assembly, and hopefully we’ll see no further problems. Teleflex engineers suggested a ground wire to the engine’s powerhead, but that would be difficult since the rigging tube on this boat originates in the boat’s lazarette, making access for a ground wire tedious.

But Teleflex engineers pointed out that my solution won’t necessarily work for every boat; again, you should first check all grounding straps and zincs and look for wires with broken insulation. It’s best to have no stray current wandering around, anywhere on your boat. And electrolysis can even be caused by current flow from outside your boat; faulty wiring in the marina, non-marine chargers on other boats, power cables hanging in the water and other sources can also cause this problem.

While my repair was done under warranty, be aware that on older rigs where the warranty has run out, replacing the steering rams can run $350 to $550. So, if you store your boat in the water, it would be a good idea to check your steering for current flow and resulting electrolysis, avoiding an expensive and potentially dangerous problem.