[C320-list] Tach running high

[Arthurpiotrowski]

Hello, had a somewhat similar issue on our “Maggie”, #330. Solution was to clean the leads of the tach wire, back of the engine, access from the aft berth. 

Sent from Artur’s phone

> On May 31, 2024, at 7:16 AM, Troy Dunn via C320-list <c320-list at lists.catalina320.com> wrote:
> 
> Jeff is correct, there is a calibration screw on the back of the tach.   If
> it hasn’t been tampered with or "adjusted" it will have a sticker across it
> with some language like "don't mess with this screw".   If your tachometer
> is getting long in the tooth there are a few things to check before you
> recalibrate the tach.
> 
> 1.  There is a ground wire and a sending wire attached to the sensor which
> sits on the back of the engine near the transmission.  Remove these spade
> terminals, cut off the terminals and reterminate the wires.   The yanmar
> harness is not marinized, it is copper wiring that has not been tinned.
> Over time moisture wicks up into the wiring through the non-marine
> connectors and corrodes.   This is true of all the terminations on the
> engine, so the same advice applies to all misbehaving senders and switches.
> (Oil, temp, etc.)
> 
> 2.  While you are at it, check that the ground wire from the sender is
> attached to a good ground.  The grounds are all terminated on one of the
> bolts for the starter.   Remove said bolt and check all ground
> terminations.   At a minimum, get some sandpaper and clean the ring
> terminals.   Better to just reterminate with proper adhesive lined heat
> shrink ring terminals.  When putting grounds back in place, remember larger
> terminations against the engine block first.  Some engines will have a
> secondary ground point near the mounting bracket near the tach sender.
> Stack them biggest to smallest from the block out, reverse order if you are
> stacking on the bolt.
> 
> 3.  If your tach 'bounces' around, you can probably get this to stop by
> turning the calibration screw back and forth a few times to wipe clean the
> contact surface inside the gauge.   Just be sure to get the screw set back
> to the same position it was in, unless of course you are going to
> recalibrate and have a flywheel pickup on hand to do so.
> 
> Good luck-
> 
> Troy Dunn
> Hull#514