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1996 Honda 50 outboard tach reads high and fluctuates at idle speed

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  • 1996 Honda 50 outboard tach reads high and fluctuates at idle speed

    I replaced the rectifier, because it was't charging and no voltage was at the tach signal line. I also tried swapping another tech,but still the same problem. I checked the charging coil output voltage with an ac multimeter it puts out higher voltage as I increase the engine speed. I need some advice what checks I could do to solve this issue.

  • #2
    Welcome to Iboats,

    Is it a digital or analog (needle) tach ? If digital it's normal that readings fluctuate at idle, stabilizes and reads more accurate when opening the throttle.

    Happy Boating

    Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers


    • #3
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      There's so much going on there. Generally, the charging coil output should be held in check (14.5v max) by a regulator. It should not allow voltage to increase beyond that, no matter the rpms. The regulator might be integral to the rectifier, but could be a separate component - depending on design. Not being familiar the the BF50's design, can't be of much more help.

      Note that a low (or bad) battery may hold charge coil output at a much lower value. Note also, all that may have nothing to do with your tach issue. The tach irregularity on idle could be the regulator turning the charge coil on and off while doing it's job trying to keep a constant voltage. You could try a known fully charged battery (13.5v) to see if that changes anything.
      Last edited by ahicks; September 25th, 2017, 07:42 AM.