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Honda tachometer issues

S

Solamar

Member
BF45
Honda VeeThree tach

The previous owner had the tach set at 4P and WOT displayed ~4500 rpm.
I changed the tach to 3P (which I believe is correct) and the tach displayed 1500 RPM at idle and 6000 RPM at WOT.

I did not believe the idle RPM so I bought a laser/optical counter that reads a reflective sticker on the flywheel. Set the idle to ~950 RPM. With the calibrate pot on the back of the tach I was able to correct the displayed idle to 950. Took the boat out on the water and WOT displays ~ 3000 RPM now...

Any suggestions to correctly calibrate the tach?
 
The tach may have been calibrated correctly.

The 3P setting is the correct setting for the BF45.

I can not address how to calibrate the tach but can suggest a potential fix for the problem. It may or may not work. I have had it work in some cases and not others. But it is cheap to try.

The early versions of the BF40 and 50 had similar issues with tachometers. The 45 has the same charging/tach circuit. The fix, was to wire a resistor between the grey (tach signal lead) and the black (ground lead). It padded down the tach signal and allowed the gauge to act properly.

Back then, Honda shipped a tach with 40's and 50's and the fix always worked with this tach. The fix did not work so well with Faria or Teleflex (now VeeThree).. I did find that it would alway work with a Faria tach, if and only if it had a build in hour meter. The fix worked occasionally with Teleflex.

The part number for the Honda resistor is 06383-ZV5-315. Others on the forum said that it is a 100 ohm resistor and have had success with that. I would recommend a 1 or 2 watt 100 ohm resistor, so it is large enough to dissipate any potential heat buildup. Here is an example http://www.jameco.com/z/CF2W101JRC-Resistor-Carbon-Film-100-Ohm-2-Watt-5-_2237247.html

Once you try the resistor, then you will have to go back to get the idle reading to agree with your optical counter.

One other issue had come up with tachs on the 45 is.... if it is located closer than 5 inches to a magnetic device, like a compass, it will not read correctly.

As I said, I can not guarantee that either of these will fix your problem, but it is worth a try.

Good luck.

Mike
 
Thanks Mike!

It is the VeeThree tach with hour meter so I might get lucky. I'll pick up and install the resister and report back.

Matt
 
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