Tach pick up on a Westerbeke 12b2

[finefurn]

I have a Westerbeke 12b2 that I think the tach is reading to high, My tach is reading 1200 rpm at a low idle. It revs up to 2400 before the engine smooths out. Where is the tach pick up on this engine and how would I go about testing for the correct reading.

[DougR]

The 12b two uses the alternator to drive the tach....normally the brown wire from the alternator provides the signal to the tach.

Use a strobe tach to check the actual engine rpm and compare that to what the instrument says. Hopefully your tach has an adjustment screw or dip switches to allow fine tuning.....

[HankOnthewater]

The pulse pickup on the back of an alternator is often marked with a "W".
If the belt is slipping the tacho reads too low.
As said in above post, use a handheld laser tachometer to measure actual RPM. If the actual RPM is lower than your engine panel indicates, than maybe the size of a pulley have been changed before you owned the boat.

Some tachometers can be adjusted on the rear to allow for a change in pulley size.