Yanmar 3YM30 rev counter reading very high

[frayedsheet]

I just had a serpentine belt kit installed to my Yanmar 3YM to alleviate belt breakage and dust problems. All is working great except for the fact that the rev counter is now reading well high. What used to be 2500 rpm is now reading as 3400 rpm (based on SOG - I dont have a digital tachometer). The alternator is about 3 years old. Its not genuine Yanmar, rather a Hitachi 80Ah.

What could be causing this and how might it be rectified?

[sailormed]

Yanmar RPM is read from the alternator. You changed the ratio of engine rpm vs alternator rpm.

[frayedsheet]

Originally Posted by sailormed

Yanmar RPM is read from the alternator. You changed the ratio of engine rpm vs alternator rpm.

So its as simple as reported engine RPM being proportional to alternator RPM? In that case I am now spinning my alternator much faster than before?