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  • Writer's pictureBill Kinney

Lesson Re-learned

Updated: Aug 19, 2022

Sometimes a lesson that we learned a long time ago is, not forgotten, but not at the front of our minds. Sometimes re-learning the lesson can get expensive.

For the first time since we owned Harmonie, the electric outhaul motor exhibited classic signs of needing new brushes:  irregular operation.  When I removed the brush holders, oddly, the brushes looked fine. Upon further disassembly the rest of the story was obvious.  25 years of accumulated carbon dust had obstructed the rotation of the armature to the point that the friction shattered the internal magnets. This motor was dead.


The outhaul motor was past saving. Fortunately the sail furing motor, which is identical, was caught in time to be cleaned up and rescued.


Amel shipped us a new motor which fit, and works, just fine. Key point here:  Whenever changing brushes do not just pull them out of the holder and drop new ones in, but clean out all the dust. Do not let it accumulate inside the motor. Do not assume that previous owners or mechanics did this correctly.

It is also important to dress and polish the commutator when changing brushes and carefully bedding the new brushes to fit. All of these steps require disassembly of the motor. Obviously, previous brush changes had been done without this care. Just dropping new brushes in without properly prepping the motor to receive them can dramatically shorten the life of the new brushes, or in the worst case, the life of the motor itself.

Lesson learned, we completely disassembled the mast furling motor (which is identical to the recently deceased outhaul motor), and cleaned the inside with vacuum and contact cleaner, dressed and polished the commutator, and tested resistances.  All checked out well, so that one should be good for the next 25 years with regular maintenance.

Other important lessons that would have saved us this cost:

  • Electric motors are (almost) forever if regularly cared for.  The furling motors hadn't gotten to the top of our list for a professional rebuild. Most of the other important motors on board had already received the "spa" treatment.

  • Take stuff apart.  You learn a lot, and this problem could have been avoided if this motor had been on my "take it apart and put it back together for no reason" list. 

Notes on the new motor: 

The new Leroy-Somer motor carries exactly the same part number, and was in all key external dimensions identical to the 25 year old original. It mounted and worked just fine. It is essentially a drop-in replacement.

The internals of the new motor are quite different, however. Key for maintenance is the fact that the brushes are very different.  Instead of two externally accessible brushes, the new design requires disassembly of the motor and replacement of the entire internal brush holder assembly because the leads for the four (not two!) brushes are welded in place to the holder.  

This emphasizes the importance of sending pictures of parts to Amel when ordering.  If you simply order brushes for Leroy-Somer motor Part Number XXX_XXX you might not get what you expect.

ⓒ William Kinney, 2020

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