Yesterday morning, I was preparing my tiller pilot (auto pilot for small boats) but it sounded like something was loose inside. When I opened it up, I found a damaged rubber sealing and the piece in the image below flying around loose. It is mechanically completely deformed and the legs are sheared off. I think it had two legs, but that's not certain. I have no clue how this could have happened, as the electronics is obviously designed around the mechanics. I cannot identify where the thing could have been on the PCB, as that looks unharmed. Also for some (magical?) reason, the pilot still(?!?) appears to work just fine.

Destroyed part Destroyed part, Side Open tiller pilot PCB, bottom side

The thing is about 5mm high and has a 5mm diameter.

What was this piece? A capacitor (what value)? I guess I should replace it if ever I find where it's missing. Elaborating on why the thing still works might be speculation, though.

The PCB (see images) looks unharmed, and the filter capacitors for the drive motor are still in place (those are very small ones, though).

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    \$\begingroup\$ Some more photos may be helpful (other angles of this component, and also the PCB). If you can't see anything missing from the PCB, then is there any chance this was never part of the autopilot device and somehow found its way in from outside? \$\endgroup\$
    – Harry
    Jun 26, 2022 at 8:42
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    \$\begingroup\$ Unlikely, the device has a waterproof sealing, as it needs to operate in rain and high seas as well. What could be is that (if it's a capacitor) it was attached directly to the driving motor as filter. But there's nothing obviously wrong there, too. I'll get some more pictures. \$\endgroup\$
    – PMF
    Jun 26, 2022 at 8:46
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    \$\begingroup\$ That component is an electrolytic capacitor; more pictures of the device are needed to assess the situation. Can you also explain how this device is powered? I think that small boats have a 12VDC system, like cars - but I might be mistaken. \$\endgroup\$ Jun 26, 2022 at 8:55
  • \$\begingroup\$ @VladimirCravero That's correct, the device operates on 12V DC. \$\endgroup\$
    – PMF
    Jun 26, 2022 at 9:07
  • \$\begingroup\$ In the last photo, there is a black rectangular connection to a tiny flat orange ribbon cable. The ribbon destination is out-of-frame. Perhaps that capacitor is associated with devices at the end of that cable? \$\endgroup\$
    – glen_geek
    Jun 26, 2022 at 11:34

2 Answers 2


It's an electrolytic capacitor. There is one place on the board with a corresponding PCB footprint and no capacitor (orange arrow).

enter image description here

It's probably the capacitor associated to the voltage regulator (blue arrow).

It used to look like that.

No idea why it came off the board, maybe a bad solder joint combined with vibrations. There's a motorized screw in there, so it probably got stuck in and squished, which would explain how it looks...

Since it's on the voltage regulator, it'll probably kinda work without it, but that will increase the chances of voltage being unstable, so your device could crash and reboot more often.

If you don't know that's a capacitor, you most likely don't have the tools to solder a new one back in, so I'd suggest bringing the board to someone who knows how to solder components. It looks like a standard 10µF or 100µF 35V cap. Doesn't look like a speial low-ESR model, just general purpose, so that's pretty easy to find.

The original should be measured with a caliper (or just the pad spacing on the board) to pick a replacement that fits.

The pads where it was soldered should be inspected carefully for damage. If they were ripped off the board, that's a problem.

Note this is a polarized capacitor, so it has to be put in the correct orientation. Normally there would be a silkscreen marking on the board to make the repair tech's life easier, but in this case there is not, so the polarity will have to be determined by looking at the circuit around it and probing for continuity between one of the pins and ground.

  • \$\begingroup\$ Thanks, that could really be it. I didn't consider the possibility that it was mechanically destroyed after it already fell off the PCB. That motorized screw has a rated thrust torque of 77kg, so very likely enough to make it look the way it does. \$\endgroup\$
    – PMF
    Jun 26, 2022 at 9:49
  • \$\begingroup\$ I do know what electrolitic capacitors are, but I've never encountered this form, and I was unsure because it does not have the capacitance printed on it. I even have some spare ones around, and a soldering iron. The main problem is that I'm rather bad at soldering... \$\endgroup\$
    – PMF
    Jun 26, 2022 at 9:51
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    \$\begingroup\$ Your assumption agrees with a previous observation: Last year, the pilot suddenly experienced the problem of regular restarts, particularly when the engine was running. I then "solved" that by wiring a new and thicker power cable. \$\endgroup\$
    – PMF
    Jun 26, 2022 at 9:53
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    \$\begingroup\$ Found this video: youtube.com/watch?v=tYc45QJNc5w. At 09:30 one can quickly see that that capacitor really should be there. One last question: Does the black marking on these capacitors mark the positive or the negative lead? \$\endgroup\$
    – PMF
    Jun 26, 2022 at 10:54
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    \$\begingroup\$ If pads are not conductive, they might be ripped off with the capactor. The picture looks like there is a copper trace leading to a pad but it has risen up. So the pads may be gone but feel free to take a photo with the pads cleary visible to confirm. Electrolytics have black marking on negative terminal. \$\endgroup\$
    – Justme
    Jun 26, 2022 at 11:29

I agree with bobflux' answer that the component is most likley a 100uF 35V electrolytic capacitor. But I think it came from pads in the large copper area near the yellow Data push-on connector.

My guess is that someone fell against the pilot and distorted the polished cylindrical guide rails within the unit. This allowed the screw-jack traveller to hit the capacitor. The guides will have to be straightened lest the problem re-occur.

Happy sailing.

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    \$\begingroup\$ The other answer provides the correct place where the capacitor was. It is confirmed by comment pointing to a video. \$\endgroup\$
    – Justme
    Jun 27, 2022 at 13:15
  • \$\begingroup\$ That's unlikely. The mechanics still works fine. Such a big mechanical shock would also have to destroy the plastic housing. \$\endgroup\$
    – PMF
    Jun 27, 2022 at 17:33
  • \$\begingroup\$ Ah. Hadn't seen the video. It looks like you are right. I was surprised that the tracks leading to the pads were so fine for a reservoir cap. Maybe they are wider on another layer. \$\endgroup\$
    – Richard
    Jun 27, 2022 at 19:22
  • \$\begingroup\$ Well. If the mechanics are fine (hurrah! hurrah!) I also guess the cap was poorly mounted and the damage occurred after it fell off. I have used such tiller-pushers; I am sure you are aware how vulnerable they are to someone falling (or sitting) on them in a seaway. \$\endgroup\$
    – Richard
    Jun 27, 2022 at 19:33
  • \$\begingroup\$ @Richard Well, I did manage to break the wooden tiller itself by falling on it... and the pilot mount was also fixed several times, but luckily the pilot itself never had a mechanical problem so far. \$\endgroup\$
    – PMF
    Jun 27, 2022 at 19:52

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