[C320-list] Instrument question

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Mar 18, 2021, 4:39:01 PMMar 18
to C320...@catalina320.com
Talk of tachs and hour meters reminded me of our problem. Our tach works just fine but the hour meter never moves. Its not a huge issue but it would be nice to have a record of engine hours.

Any suggestions of the cause or cure would be great!

Tangled 226

P.F. Ross

Mar 18, 2021, 5:21:36 PMMar 18
to C320...@catalina320.com

It has been a while, but I had the same problem (tach fine but no eng
hrs). Took tach apart, but decided just to buy a new one from Catalina

Your hull is close to mine, so you may have a Perkins like I do. In that
case, there is no mag pickup so you need to choose the alternator sensing
model, Z4682. Even though this tach description calls out "Yanmar", I
figured any tach that uses alternator pulses would work, and I was largely

Check out the "Read More" section on the tach on the CD website and you
will see there is a selector switch on the back that accommodates various
alternator poles and pulley sizes. I then used a handheld tach (also sold
by CD, Z371) and calibrated the tach according to the procedure. The
selector switch adjusts the "slope" of the calibration curve and the
calibration screw adjusts the "zero". At least that is what we called them
back in the dark ages when I worked as a young engineer with GE building
power plants.

I find that the discrete selections on the switch do not allow a perfect
slope on my engine, so I choose an RPM to adjust to, in my case 3000,
IIRC. So I know that at 3000, I am dead on and on either side, just
slightly off.

I also know for sure when I am below 1000 RPM because I get the "Perkins
Rock n Roll"!

Frank Ross
Beta Wave #206
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