Extracted from : Ocean Navigator No. 51

Frustration fuels starter motor repair

by: Marcia Reck , Bremerton, WA

To the editor:

Those who regularly put to sea in small vessels usually become handy at fixing almost everything aboard. The ability to jury-rig one piece of gear or another can keep one’s vessel functioning. For this reason, voyagers learn, often the hard way, to carry a wide range of spare parts.

There are some parts of the voyaging sailboat, however, that tend to defy the efforts of even the most resourceful sailors. Many such problems are linked to the iron monster that lurks in the bilge. Starter motors, for example, seem to be a prime offender. Salt water finds its way into the engine compartment, and from there into the starter. Even if the starter is promptly cleaned, the resulting deterioration of the coil insulation can be like a time bomb. The starter may fail years later, often far from land. As starter motors are expensive, few of us carry spares. Moreover, starters are one of those components most sailors feel incapable of repairing on their own.

My husband Dave and I have been living and cruising aboard Mañanaa 35-foot Fuji cutter, for 12 years. Despite plenty of experience with breakdowns and jury-rigs, when our starter failed in the Aleutian Islands, we too thought ourselves helpless. While Dave has good mechanical skills, he had always considered a major starter repair to be beyond his abilities.

The starter on our boat is a shift lever, Delco-Remy unit, a type commonly found on marine engines. It was one of the few parts of our 18- year-old Westerbeke engine that we trusted. True, it had once been thoroughly soaked in salt water thanks to a faulty oil cooler. Three years after that dunking, it began shorting out. We were then preparing to depart Fukuoka, Japan. We immediately found a repair shop which, we were assured, specialized in rebuilding starters. It came back to us freshly coated with bright red paint, supposedly rebuilt and good as new. And indeed, for three months it performed flawlessly. Then, as we made landfall on remote, uninhabited Kiska Island, it failed.

AT LEFT : This diagram shows the internal structure of a starter motor, with field coils visible below the armature. The problem with the author’s starter was caused when insulation on the field coils corroded and some wires shorted-circuited against the starter casing.

We first checked the voltmeter to verify that our batteries held sufficient charge to turn over the engine. Dave then checked all of the wiring to the starter and determined that it was in good condition. He next removed the starter unit, and, using a multimeter, determined that it was again shorting out. He checked the solenoid, which was in proper order; the problem, therefore, lay in the starter motor itself. He also quickly discovered that he had no hope of repairing the motor without removing eight large screws. These attached the pole shoes to the housing, and unless they were removed, it was impossible to gain access to much of the internal workings of the starter motor. According to the engine manual, which he immediately consulted, the screws can be removed only with a very large impact screwdriver, a specialized tool which we did not have on hoard. The only other option was to drill out the screws. This, Dave felt, could not be done without an electric drill, requiring far more power than was available from Mañana‘s batteries.

We saw no alternative but to sail to the nearest port where we might seek assistance. The closest inhabited island was Adak, sume 300 nautical miles to the northeast. The island is the site of a U.S. naval base. Although the authorities there are generally inhospitable to voyagers, we hoped they would at least allow us to stop long enough to effect repairs. We weren’t particularly comfortable with such a course of action. Like many voyagers, we are rather proud of our ability to get out of predicaments on our own. We didn’t at all like the idea of having to throw ourselves on the mercy of people who didn’t even want us in their harbor.

In any event, we were spared the humiliation. Not only couldn’t we get anywhere under power, we couldn’t sail much of anywhere either. For the first 24 hours after the starter failed, we were able to sail in the desired direction at about four knots. Then the wind lightened, allowing us to make but one to two knots at best. For two days, we watched the same island play peekaboo with a fog bank. Driven to action by boredom, Dave took the starter off the engine once more, only to reach the same conclusion: there was little else he could do at sea.

If necessity is the mother of invention, perhaps frustration is the father. After 12 hours of being totally becalmed, Dave decided he simply had to make the effort to get the starter apart. Using what tools he had aboard, he would do his best to remove the eight screws. Further impetus came from our previous experience with the Aleutian weather. We knew it was only a matter of time until the calm switched abruptly to an easterly gale. We had no desire to wait around to be blown back to the west. In addition, slatting of the mainsail in the light conditions had caused the gooseneck to break, and we didn’t wish to test our jury-rig in rough conditions.

The tools at Dave’s disposal were a hammer and set of chisels, and a brace. The latter is perhaps not part of the average sailor’s tool chest, but it should be. Far more force can be applied with this tool than is the case with the standard hand drill.

Dave feared he lacked the skills to repair the motor itself, even if he could get the housing apart. But removing the screws proved to be by far the most demanding part of the operation. While I braced the unit, he began by attacking a screw head with a large cold chisel. He then alternated between drilling and chipping away at the head of the screw with the hammer and a smaller chisel. This process, of course, damaged the head of the screw. As we didn’t have any replacements on hoard, we tried to avoid destroying the heads completely, hoping to leave them sufficiently intact that the screws could he reused.

Each screw took around 45 minutes to loosen. We were extremely fortunate to have calm seas throughout the operation. The work would have been infinitely more difficult in choppy seas as it was essential to hold the starter motor immobile.

When all the screws were finally removed, and the casing apart, the general problem, if not its actual location, was readily apparent. There was a very distinctive burnt “electrical” smell.

A starter is basically an electric motor. Inside the casing are four pole shoe magnets that are wrapped with coils of wire called field coils. When electrical current is passed through the field coils, the pole shoe magnets are turned into electromagnets and a strong electrical field is created. Meanwhile, current is also passed, via the brushes, to other coils of wire wrapped around the shaft of the starter. This assembly of coils is called the armature. When current passes through the armature, a second magnetic field is created. This opposes the field created by the pole shoe electromagnets and the interaction of the two fields causes the armature and the shaft to spin. On the shaft is a pinion that engages with the flywheel and cranks the engine. A short circuit, i.e., metal touching metal inside the housing, interrupts this sequence. Faulty brushes can also stop the process. If they become worn, they must he replaced, hut this is unlikely to happen within normal engine life. (Brushes, actually small pieces of graphite, are small and inexpensive; it’s easy to carry spares, and we do.)

In a marine environment, a short is often caused by salt water-induced deterioration of the insulating cloth wrapping on the field coils. Once the wrapping starts to disintegrate, the metal of the field coils makes contact with the metal of the housing. This is what happened to our starter. Once the housing was apart, the deterioration of the wrapping was all too obvious. On three of the coils, little more than shreds of wrapping remained. Also obvious was that we had gotten little more than a shiny paint job for our money in Japan. The supposed experts had apparently randomly stuck shims of bakelite or a similar material between the coils and the casing, moving them around until the shorting stopped.

The job had never been done right. Now, with the wrapping further deteriorated, it might as well never have been done at all.

Using the multimeter, Dave began to search for the exact location of the short. (This diagnostic tool is another item no voyager should he without. Ours has proved its worth many times over in tracking down electrical problems.) Each time he thought he’d found the short, we’d attempt to isolate the spot using one of the shims. Gradually it became clear that there were multiple shorts. Using electrical tape, Dave carefully rewrapped each of the three suspect field coils. We then reassembled the unit, again using the multimeter on each coil to verify that there were no shorts. With all four coils back in place, there was still no current flow and things looked good.

Using pliers and the hammer and chisels, this time to tap and guide, we were able to reinsert and tighten the damaged screws.

Reinserting the armature into the housing proved to be a tricky operation made only slightly easier by two sets of hands. it is very important not to crimp any of the wires leading to the brushes. In addition, the brushes must make proper contact with the commutator.

Dave reinstalled the starter on the engine; I think we both held our breath the entire time. He then turned the ignition key and the engine fired on the first try. I’m quite sure neither of us has ever heard a sweeter sound.

Although a scenario such as ours is among the most common with starters aboard voyaging yachts, there are other possible causes of malfunction in addition to shorts and faulty brushes. Before attempting to take a starter unit apart, first determine that the batteries hold sufficient charge to enable the engine to turn over. If engaging the starter with properly charged batteries produces only a clicking sound, chances are the problem is in the starter solenoid. If, however, batteries are charged and all electrical connections are okay, but engaging the starter causes high current draw without actually starting the engine, the problem is almost certainly within the starter motor itself.

Double check all wiring and connections, including connections to and contacts within the solenoid. Elimination of these possible sources of trouble again points to a problem within the starter motor.

Once the motor has been dismantled, if there is no obvious deterioration of the coil wrappings, the commutator should be cleaned. This is best done using a knife to scrape out the lengthwise grooves, then polishing with fine sandpaper.

If the engine is turning over slowly with high current draw, other possible sources of trouble include too much friction resulting from tight, dirty, or worn bearings; loose pole shoes allowing the armature to drag; or a bent armature shaft. Bearing problems can generally he remedied by disassembling the motor and cleaning everything well. Use fine sandpaper to polish the shaft, and oil it. Loose pole shoes should be tightened. Unfortunately, if the shaft is bent, the only alternative is replacement.

Failure of the engine to turn over at all with a high current draw indicates either a direct short in the terminal or fields, or frozen bearings; in the latter case proceed as for dirty bearings.

As we learned, starter failure at sea need not cause a mariner to despair. The essential tools are simple ones. Diagrams and an explanation of your particular starter motor are of great value in helping to understand what may be wrong and in pinpointing the difficulty. Otherwise, starter repair at sea often requires nothing more than basic mechanical knowledge and a healthy dose of determination.