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In Bayliner boat OMC stern Drives, the trim sensor used an Allen Bradley potentiometer/rheostat. The number on the back of the case is: 984246 8821 J. I believe it is a reverse log design with a 'D' shaft. I'm not sure I can trust my measurement as this was in a submerged environment and no longer functions in-circuit as designed, but it has only two solder lugs. Is there a way to find a current day substitute?

Tony Roussos
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  • Please remove your email address from your post. Quite apart from making it available to spam harvesters, all answers to questions are to be posted on the site, not through private correspondence. – Transistor Jul 14 '19 at 11:24
  • What did Bayliner or Allen Bradley say when you asked them? – Andrew Morton Jul 14 '19 at 15:31
  • An old data sheet indicates that A-B assigned special part numbers to potentiometers with special features. The one you have may have a unique number because of special features. That probably means the design details can not be determined. Even a rheostat with two solder lugs may have a special number. A non-standard shaft and bushing could also get a special number. You may be better off searching for OMC replacement parts. –  Jul 14 '19 at 15:36
  • A-B Datasheet PDF http://www.farnell.com/datasheets/1580637.pdf –  Jul 14 '19 at 15:37
  • Bayliner said my boat is too old. Their records don't go back to 1989. Allen Bradley is defunct. A company called Sierra Marine is now offering trim sending units at $150+ a bit costly. I called Sierra Marine tech support, but they will not say the value or composition or supplier of the pot. – Tony Roussos Jul 16 '19 at 17:10

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If you carefully dismantle then pot and use electrical contact spray you may be able to get an unloaded R measurement as a percentage or the max outer lead R ratio.

From page 192 on the linked data-sheet, kindly commented by @Charlescowie, you can see which curve fits the result of your $5 DMM reading.

If you are really good, you can dismantle the Pot and restore it to like new performance with rubbing alcohol and very light fine abrasives. Then reassemble all the moving parts to exact position and reconnect.

Tony Stewart EE75
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