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Siler Starum's picture
Siler Starum
Joined: 4/20/18
Posts: 58
range switch setting tachometer

I replaced my broken tachometer for a new one, delivered through Catalina-Direct.
The new one delivered shows on the ID-plate: 2051 rpm @ 400Hz and a range switch which is set at "B".
However the old broken one shows on the ID-plate: 2797 rpm @ 400Hz. and has no range switch like on the new one.
The range switch on the new tachometer is going from "A" to "E". 
To which position should I set the new tachometer so that I am sure that the revs from the engine are shown correct on the tachometer?


Durk Nijdam
Catalina 36MKII - 2001 / hullnr. 2013
Stavoren - Holland

Stevenjones's picture
Joined: 6/29/07
Posts: 74

Catalina Direct has an excellent tech help desk -a separate phone number.  I'd suggest calling them. Happy New Year! 

Siler Starum's picture
Siler Starum
Joined: 4/20/18
Posts: 58

My question has been answered: information received from CatalinaDirect.

Tachometers are adjusted by our vendor to be approximately correct when installed on an M25XP with standard alternator and pulleys. They can only be exact if calibrated after installation using a mechanical tach or strobe. All other engine installations including other Universal Diesels and Westerbeke engines may require adjustment of the tachometer.
A fine calibration potentiometer is under the sticker at the back. It is a delicate electronic device mounted to the far side of the circuit board. A watch maker can successfully adjust it without damaging it or pushing it off of the circuit board. Our experience is that most mechanics are too ham-fisted and will break it every time. If approximately correct isn't accurate enough and you remove the sticker over the calibration screw, the warrantee is void.
For Universal M-25, M-25XP, M-25XPB, M-35, M-35B: set "Alternator Range" to "B" then tune with hand tach

Catboat Willy's picture
Catboat Willy
Joined: 12/22/14
Posts: 292

Thank you for posting that information. I installed a new tachometer several years ago and had a difficult time figuring out  what position of the switch was the correct one. I wish I had your information at the time. After calibrating the engine with a strobe tach, we found the tachometer to be less than 100 revolutions off and decided that it was not worth fooling with. I was also told that it takes a special screw driver to adjust the screw that lies under the label.
 Happy New Year,

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