Re: Can i hook up a tach? 71 40hp johnson.
Chances are that the tach mounted in your boat won't work with your motor. Most currently used tachs operate from a signal sent to them from the rectifier on the engine. Since your motor does not have an alternator type charge system, and has no rectifier, you're out of luck.
There is, however, an alternative - an inductive tachometer. The most commonly used unit is a Tiny Tach. Here's the link to the company's site ...
http://www.tinytach.com/
There are also tachs that will read a magnetic pickup, which is mounted at the flywheel ring gear. These units tend to be somewhat expensive, but the guage might fit in place of the unit that you have in your dash now. Here's a link to one manufacturer ...
http://www.fwmurphy.com/pdf/MT-9004B.pdf
Your speedo will probably work when you get a new pitot tube installed. You may find, however, that it isn't very accurate. I have found that when checked against a hand held GPS, mine is off by 2 - 5 mph.
