Tachometers

Hello, I've tried to think about this, logically before asking. My initial conclusion is...there is no difference, but, here goes. On my 2-25, The Yanmar single cyl diesel needs a tach. A 0-4,000 is adequate. I think a pickup off the flywheel is more precise, assuming i can find the proper magnetic sensor, than running off the alternator, but, the question is...does it HAVE to be a Yanmar tach? Is there a differnce between a Faria for a Volvo diesel or a Yanmar diesel? Its only measuring rpm at the flywheel. Feel free to edumicate me before i spend the $$. 🙂 Thank you. ..tom