Inaccurate Tach...

[scottrbishop]

I have a 1973 Merc 850 that came with a boat I bought this spring. I've spent that last few months fixing various problems and I've now come to the conclusion that my tach is inaccurate. At idle it reads about 700, but WOT reads only about 2500. I've hooked up an ignition coil tach and it reads 5200 at WOT. I've replaced the voltage regulator which helped my battery charge but did not fix my tach. It reads the idle correctly and always moves up when I increase the throttle, but it doesn't give me accurate readings. Does it need replacing or is this a common problem that could mean something else?

 

[Laddies]

Re: Inaccurate Tach...

Ck the back of the tach and see if the set arrow is on 6 pulses, if not reset it if it is buy a tach