how to check accuracy of tach?

[hammer250v8]

i don't think my tack is working right.<br /> is there a way to check it? i have a 1991 evinrude V8. it works great up to 6000rpm then stops there.i'm playing with props and trying to reach 6700rpm.i had a 19 pitch 4 blade and 6000rpm. i exchanged it for a 17 pitch 4 blade of the same make(power tech OFS series) and still only get 6000rpm!somone suggested i might not be getting enough air into my motor. my cover dosn't have the vents on the side like the 300 V8's do.thanks for any advice ....james

 

[Spidybot]

Re: how to check accuracy of tach?

Try using a service tach for comparison. Even the cheaper auto-tune devices are fairly accurate.<br /><br />What is the max recommended rpm at wot for your motor?

 

[walleyehed]

Re: how to check accuracy of tach?

If you don't think you are getting enough air, due the same thing we do when checking for exh. leaks and run WOT with cowl off........