Electrical Fire! (and some lessons learned about starters)

3 Jan

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Voice Mail: “Hi Clark, it’s (name withheld). I was out sailing today with my daughter and we had an electrical fire on the new starter you installed. Because of the fire we lost the engine and hit the south tower on the Golden Gate Bridge, called the Coast Guard, and had to be towed back to our berth. When I opened the engine compartment there were six inch flames rising from the starter, but I was able to blow them out. I don’t know where that leaves us, but I’d sure like to speak with you.”

Not what a marine electrician wants to hear. After my initial panic, I reflected that this was a basic R&R (remove and replace) of an old starter for a new one. I’d tested it several times, by cranking and starting the engine, and all seemed well. Various scenarios flew through my mind – defective starter, defective solenoid, some sort of shorted wire, stuck solenoid or stuck starter button, or, eh gads, installer error. I called the owner, who was very understanding, and was back on his boat the next day. If you look at the photo above, all the insulation on all the wires leading to the starter is fried, and was burning until he blew it out.

After an initial check, I called the owner and told him that no matter whose fault it was, the damage was probably less than the deductible on his insurance, and that I might as well remove the starter and start the replacement process. He agreed. I pulled the starter and found it well-burnt, and the solenoid completely melted, with both of the studs loose. The main linkage between the solenoid and the starter motor had acted as a fuse, melted through, and ended the fireworks:

I took it back to the starter store, where they were very understanding and agreed to replace it under warranty, but also opined that something had probably got stuck, and that the starter probably wasn’t at fault. They noted some damage to the pinion gear, which I hadn’t noticed.

I installed the (second) new starter and continued my postmortem, finding very quickly that the cranking circuit was closed, as in, if I’d connected it the starter would have started cranking and wouldn’t have stopped. In this instance the boat had a starter button, separate from the key switch that energized the circuit, and the button was stuck:

Blessed sweet mother of God, it wasn’t my fault! I replaced the button, and the burnt wires, tested it all out, and all was well, for the second time. The owner was very understanding, ended up buying my wife and me a nice bottle of wine, and we decided we owed the guys at the starter store a case of beer.

There are some interesting things that happen with a stuck starter, one of which I didn’t know about. I knew about shorts, of course, and 98% of high amperage starter circuits aren’t protected with fuses, so these can be spectacular. And I knew about all kinds of unintended open circuits, as with bad motors, bad solenoids, etc. But I always thought that a stuck starter, as in, a starter that stays engaged after the engine starts, would just burn out its innards or strip its pinion gear.

Nay. A starter that stays engaged after an engine starts gets spun continually, much faster than its intended rotation speed, and actually becomes a generator, sending high current back into the electrical system. In most cases the batteries and cabling can handle the current, but the starter can’t. It gets very hot and finally burns up (from high current, rather than friction, overheated brushes, or whatever). Even in normal use a starter is an intermittent duty motor: With a recalcitrant engine you should only crank it for ten seconds or so at a time, then give it thirty seconds to cool off, and to allow the surface voltage to come back on the battery.

So, it is very important to make sure your starter disengages after your engine starts. In most cases this is obvious, as in your car, where if you held the key in the cranking position, or the starter got stuck this way, you’d hear it. But on many boats it’s not so obvious, since the engine panel might be some distance from the engine, and once started the engine noise can drown everything else out.

This boat happened to be a Catalina, and on Catalinas it’s standard to have a starter indicator light on the instrument panel. This is a good feature, and not common on other boats, but you’ve got to know it’s there:

On this boat it was there and still worked, but the owner didn’t know about it, plus it’s hard to see in daylight, and easy to miss in full combat mode (they were close to the south tower of the Golden Gate Bridge in an outgoing tide, after all). But also on Catalinas, and many other sailboats, the engine panel is exposed to the elements in the cockpit, sometimes gets kicked a lot, and generally takes a beating. In this case the starter button saw constant rain and spray, and eventually corroded and got stuck.

On my boat I’m standing right over the engine when I start it, so I’d hear it in a nanosecond if my starter got stuck, but not so on many boats. If it wouldn’t be obvious to you if your starter got stuck, you should consider an indicator light or buzzer. When you consider that it would result in not only a destroyed starter, but in not being able to start your engine again, and maybe an electrical fire, it’s worth some thought.

This article was syndicated from The Adventures of the Vessel Condesa


  1. Neiallswheel

    You can get trip inline fuses , I got a 40amp version from eBay, for a camper project.
    on some cars like BMW’s replacement fuses are £10 a go.
    I found this page, coz I’m having problems with my cars starter circuit. Thanks for all the info. Cheers

  2. John Henderson

    Well I wish I had read this two days ago! I can confirm, not easy to catch on a Catalina 36. Thankfully, no fire, my wife said “there’s a noise in the engine”, so I took the cover off and saw the starter engulfed in smoke. Fried the starter, but thankfully in the slip. The button was stuck 3/4 of the way out. Very easy to miss.

  3. Ken Kloeber

    Thanks Clark,

    I suppose the best is to have a switch that kills power thru the start switch (in case the button/key switch gets stuck) and a switch to kill power in the starter cable (in case the solenoid get mechanically stuck in.) Relying on the 12BO switch could be disastrous, killing power to everything. That wouldn’t necessarily save wiring right at the starter when it turns into a generator, but at least it will isolate it all from the rest of the boat wiring.

    BTW, all the old Universal harnesses should be retrofitted with a 25 or 30 fuse on the panel power feed wire, within 7″ of the solenoid “B” post (I use a 10 awg ATC weather tight fuse holder.) I won’t EVEN get into all the other fixes that must be done on those harnesses.


  4. Clark Beek

    Hi Ken, Yes, the battery cable to the starter was fried. Hard to tell which wire actually caught fire first, as the insulation was burned off all (battery cable, S wire, feed to panel, alternator output). All wires were still intact, but the jumper between the solenoid and starter wire melted, as shown. Something must have finally melted inside the solenoid too, otherwise it would have kept drawing current just to keep the solenoid energized. The done thing seems to be to put a fuse somewhere along the engine panel positive feed, and hope that this would protect some mishap with the S wire, engine instrumentation, glow plugs, and whatever else is fed from the panel. In reality each of these circuits should probably be protected individually, as they all have different currents and different wire sizes, but nobody does it that way. It’d mean a real tangle of fuses. The alternator seemed to be unaffected, at least it was still putting out juice at a reasonable voltage/amperage.

  5. Ken Kloeber

    Very interesting about the starter light — I always thought that was pretty useless on the panel (own a C-30.) But now I’m thinking a piezo alarm on the “S” circuit may be in order. The annoyance of a few seconds of an alarm would be far preferable to not knowing that the starter stayed engaged!!

    Upon inspection, was the charge wire from the Alt output also fried? Wouldn’t the overcurrent have damaged the Alt?

  6. Ken Kloeber


    Was the pos battery cable fried? I don’t see it in the photo.

    I see one commentor noted he installed a fuse on the “starter wire,” which I presume he means the “S” wire. I don’t see that it would have prevented the fire, as the back-amperage would have been thru the battery cable/”B” terminal — and the “S” wire: was simply maintaining the solenoid in the engaged position with overcurrent condition. The “S” wire looks to be intact, with the insulation charred from the fire, but the copper not melted from overcurrent. Do you see it that way also? Older Catalinas have an OEM fuse on the “S” wire, which is totally useless. The fuse belongs on the cockpit end of the harness. The only good that fuse does, is if the wire falls off the solenoid–and falls against the block, while cranking the engaging the key the fuse would blow. An unlikely event. The better solution is a breaker on the panel that protects everything past the panel, and a fuse on the power feed to the panel (on the 10 awg cable within 7″ of the solenoid “B” terminal.)

  7. Clark Beek

    Hi All, I go into the starter fusing issue ad naseum here. In short, the ABYC allows ONE circuit to be un-fused on a boat, and that’s the starter circuit. This is because the ABYC standard covers boats up to 100 feet, and some of those bigger boats may have starting circuits that are of such high current they can’t be fused. (I think 400 is as high as class T fuses go.) For the rest of us, with engines up to, say 150HP, we should fuse our starting circuits along with other high amp connections.

    Yes, the right thing to do for a stuck starter is kill the engine and investigate, and hope you aren’t drifting toward the rocks. For a diesel this is usually a fuel shut-off; for gas engines killing the ignition. Then if that doesn’t do it you need to de-energize the main feed to the starter by whatever means.

    Beneteaus and other European boats have much better electrical systems. There must be an actual code requirement in Europe, thus the T switches every which-way, including on the negative side, making for a quick and sure way to kill the juice.

    A stuck starter could be caused by a stuck starter button or key switch, a stuck solenoid, or a stuck pinion gear, then many systems have a secondary starter relay (secondary to the solenoid, which is also a relay), which could also stick. In short, many roads to this mishap.

    Also a good skill to know how to start your engine by jamming a screwdriver between the right combination of contacts on the starter/solenoid, should all else fail.

  8. Michael Quigley

    The article doesn’t mention how to respond to this emergency. On my Beneteau 343 I can disconnect the positive cable from the start bank by turning a red T-handle. I suspect other males could do the same by selecting “off” with the battery bank select knob. Hopefully, this would remove power to the starter. But if it has already transformed into a generator the only thing to do is shut down the engine immediately. The Beneteau has a manual fuel-shutoff handle right next to the electrical handles. Sounds like my new emergency procedure is to shut off both fuel and electrics to the engine ASAP.
    Hi Bob!

  9. Harry Juris

    After reading the article I googled “Catalina starter indicator light” I came up with a November 2001 PDF from Seaward who is the OEM for panels for Catalina. The PDF describes various “upgrades” made to 1993 and later panels to make them compliant with a standard that Catalina and Seward agreed on. One of the changes was the elimination of the starter indicator light. It does not indicate why the did that.
    The PDF can be found here:


  10. Bob Atkins

    Great article and a more common problem than many realize. Ideally it would be much better if boats were equipped with a starter disconnect that would automatically break the connection with the starter either after a certain number of seconds or if the circuit sensed some back feed of voltage from the starter.

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