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Posted by member Kenny Clark on Friday 3 October 2025

This may be of interest to anyone that has experienced a problem with faulty RPM reading.

The needle on tachometer was erratic to say the least. RPM needle would indicate normal reading at 10knts for a couple of seconds then keep jumping between 4000-6000rpm for no apparent reason even though boat speed over the water remained constant. Eventually reading would normalise for a while then a minute or so later the needle reading would drift all over the place.

By chance I came across a fix that was remarkably simple. I took off the back panel to instrumentation, steering gear to look at tachometer, looking for inspiration to solve the problem.

My fix – There is a round black dial on back face of tachometer (see photo) that should be set to suit the engines capacity 4,6,8 cylinders etc. My BF75 Honda outboard was correctly set at 4 on the dial – I simply inserted small screwdriver and gently turned the setting all the way clockwise stopping at each setting in turn, then back again a few times, back to setting 4. After running the engine again, the RPM needle reading seemed back to normal.

So far so good. I will keep an eye on this to see if this is a permanent fix.

Kenny

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