Tachometer Sensor Preferences

[Rusty123]

My Yanmar 2QM15 has a Faria tachometer with a magnetic pickup. It's not very accurate though (reads 2100 when engine is actually at 2500). Not sure if calibration is possible, but since I'm in the middle of an alternator/regulator upgrade, I could easily switch to a tachometer with electronic input, and abandon the magnetic sensor.

Any reason to choose one type over the other? Is one more inherently reliable or accurate, for instance?

[Viking Sailor]

Something I found interesting:

Design Technology, Inc., Home of Tiny-Tach - The Tiny-Tach Line of Tachometers

Regards,

[ranger58sb]

Originally Posted by Rusty123

My Yanmar 2QM15 has a Faria tachometer with a magnetic pickup. It's not very accurate though (reads 2100 when engine is actually at 2500). Not sure if calibration is possible, but since I'm in the middle of an alternator/regulator upgrade, I could easily switch to a tachometer with electronic input, and abandon the magnetic sensor.

Any reason to choose one type over the other? Is one more inherently reliable or accurate, for instance?

I believe it's not the sensor, but rather the Faria tach technology.

First, though, your tach is likely adjustable, in case you didn't know. There should be two adjustments on the back, one course (a range of flywheel teeth) and the other fine... so you can dial it in using a hand-held tach to calibrate. That said, our Faria tachs are therefore most accurate at 2000 rpms (the set point I used), not as accurate at 600 (idle) and 2600 (WOT) RPMs.

Second, Aetna Engineering makes electronic tachs that are said to be accurate to within 1 RPM... and one version can use the same magnetic sensor you have. I know of an owner who changed his tachs from Faria to Aetna and he's been very satisfied.

-Chris

[Blue Stocking]

When doing your Alternator/ Regulator upgrade, make sure your 12 pole alternator (most Balmars) or the 14 pole DelcoRemy unit is compatible with the regulator you choose. I have spent a considerable amount of time trying to get a Delco 10 si with a Balmar ARS-5 to read correctly on a Perkins 4-236 tach. Throughout the rev range, tach is slow.