[C320-list] Tachometer Problem

[Allan S. Field]

Note that the C320 Association has a laser tach as part of the toolbox
loaner program.

-----Original Message-----
From: c320-list-bounces at lists.catalina320.com
[mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Melissa&Larry
Leibman
Sent: Friday, July 10, 2009 9:14 PM
To: c320-list at lists.catalina320.com
Subject: [C320-list] Tachometer Problem

Jamie,
 
You may have already rectified the tach issue but if not, I have been having
the same behavior for several months. I finally got around to checking into
it beginning at the tach sender on the instrument housing and working up to
the tach itself. I've uploaded a few pictures at:
 
http://www.catalina320.com/mediagallery/album.php?aid=214&page=1
 
It appears at least on Easy Going that the problem was at the tachometer. If
you check out the picture at the link below, there is a calibration
adjustment on the left side of the picture but on the right side is a kind
of blurry black dial adjustment. I believe that adjustment allows you to set
the number of teeth in the pinion gear. From the labeling around the dial I
expected it to have 3 positions. However, it just turns continuously with no
obvious detents. As the engine was running I adjusted this dial and at
certain points the tach would jump much like I would observe while running.
I adjusted within the first range/position until the tach appeared to give a
stable reading. I figured I would also need to adjust the calibration screw
but when I rechecked the tach with a laser tach, the readings appeared to
match within the precision of the tach in the cockpit. I then ran the engine
at several rpm settings and all seemed to agree well with the
 laser tach. Previously my laser tach gave readings 100-400 rpm lower than
the cockpit tach depending on the speed. 
 
http://www.catalina320.com/mediagallery/media.php?f=0&sort=0&s=2009071017503
760
 
I haven't had a chance to take the boat for a spin so I'm not certain if the
problem is really solved but so far so good.
 
Larry