Used on the following boat/engine combinations:
• Catalina 270 (Perkins M-20)
• Catalina 320 (Perkins M-30)
• Catalina 270, Catalina 309 (3YM20)
• Catalina 320, Catalina 355 (3YM30)
• Catalina 375, Catalina 385 (3JH5)
• Catalina 387, (3JH4)
• Catalina 400, Westerbeke 42B
• Catalina 400, Catalina 42 (4JH4)
• Catalina 445 (4JH5)

There may be other applications where this tachometer was used as well. It will also work with most higher output after market alternators. Your alternator must be equipped with a pick-up "tap" on the back of the alternator. You must adjust the tachometer by first determining the pulley ratio and number of poles in your alternator. To assist in your decision and to calibrate to your alternator, refer to the table on the page labeled 337 provided below under "Technical Support". You are responsible for determining if the tachometer is suitable for your alternator before ordering. All sales are final for tachometers used on after market alternators.

• Nominal size: 3" diameter
• Bezel diameter: 3-3/4"
• Cutout: 3.4"

1) Our tachometers are adjusted to be approximately correct (within about 50 RPM) when installed on an engine with standard factory installed alternator and pulleys, selected from the drop-down menu above.

2) When you order this special order item it sets off a chain of events like Willie Wonka in the chocolate factory. Once you turn the valve the chocolate is coming down the pipe. If you then decide you want caramel, the chocolate is still going to come out of the pipe. We can't put the Chocolate back in the pipe, so someone is going to have to eat it, and it's not going to be us! Your order can't be canceled, returned, or magically changed into caramel, so please order carefully the first time!

3) A fine calibration potentiometer is under the sticker at the back (click on the additional images below the main image to the left). It is a delicate electronic device mounted to the far side of the circuit board with three soldered on contacts. A watch maker can successfully adjust it without damaging it or pushing it off of the circuit board. Our experience indicates that mechanics are too ham-fisted and will break it every time. If approximately correct isn't accurate enough for your needs, you can attempt to adjust it using a jeweler's flat blade screwdriver (not Phillips head). But once you remove the sticker over the calibration screw, the warranty is void and the tachometer cannot be returned.

4) Early Yanmar engines used a magnetic pickup adjacent to the flywheel on the bell housing. This OEM style tachometer with hour meter is no longer available for a magnetic pickup. But most Yanmar alternators have an AC Tap or tachometer terminal on the back. Just move the wire that connects to the flywheel pickup to the proper alternator terminal and use the technical support article Engine Instrument Technical Information for more details on adjustments needed.

5) If your Perkins engine has a tachometer with a rotary ABCDE "Alternator Range" switch, call us with with the setting of your current tachometer. We will use the same setting and custom adjust a tachometer for you using our electronic signal generator.

6) Each tachometer is bench tested before it leaves. This leaves the indicator at a position other than zero. Once you install the tachometer, the indicator will return to zero when the engine is stopped with the "Stop Engine" handle before the ignition is switched off.