Calibrating the taco on a Yanmar 4JH4E?

[Ian_Edwards]

I upgraded the alternator on my Yanmar 4JH4E last year from 80 amps to 150 amps with an Eclectromaax system, including changing the belt drive from a V belt to a serpentine belt.

This changed to pull ratios, and now the Taco reads to high. I have an optical strobe, so I can measure the RPM at the flywheel.

I get 714 rpm on the strobe at idle, the rev counter reads 820 rpm, and winding it up a bit, I get 1615 on the strobe and 2000 rpm on the taco.

I've yet to figure out how to re-calibrate the Taco, I get varying, and conflicting bits of info' from google searches, including a reference to a Yanmar technical bulletin MSB 03-015, which I can't find.

Has anyone done this and can provide any guidance or point to some instructions?

The engine is from 2007, has a type B instrument panel, with an analogue Taco and an LCD engine hours display.

 

[VicS]

I'd expect to find an adjustment screw on the back of the tacho. Maybe sealed in some way or hidden by a paper label

 

[jiris]

I'd expect to find an adjustment screw on the back of the tacho. Maybe sealed in some way or hidden by a paper label

Or, in the case you get totally desperate, create your ow new "face" for the tacho. That is what I ended with after a long and fruitless experimenting. Not as big deal as it look, depends really how tidy you want to have it.