Some buy a tinytach.com tach, I bought this which is similar and only $ 13, just got it and haven't used it -http://www.amazon.com/Penny-Tachometer-Stroke-Outboard-Mercury/dp/B00ACDP6YU/ref=sr_1_5?ie=UTF8&qid=1401556117&sr=8-5&keywords=tachometer+boat I'm gonna use it to verify the accuracy of my console tach.