Tachometer calibration

[K_POPE]

At idle my tach reads 200 rpm...i know that's not correct. How do i calibrate the tach and what is the normal idle rpm for a 1990 351?

[jimmer2880]

maybe it's the connection. I'd clean both ends first & see if that fixes it.

[K_POPE]

Could that cause it to read low? If the connection is bad wouldn't it not read at all? Also where is the tach connection at the motor?

[BrianM]

The idle should be about 650 to 700 rpm.

[whitedog]

Tach connection should be at or near the coil. If the connections are dirty it will have low voltage and this could cause a low reading.

[K_POPE]

Should i just get a new coil? It looks really old and there is no telling when the last time it was changed. (just bought the boat couple weeks ago)

[jimmer2880]

if you're not having other issues, I'd just clean the contacts & use the existing coil.

You can do what you want though (obviously)....

[dchatagnon]

I have the same issue. Is it a grey wire for the tachometer? Is it plugged to the positive or to the negative connection of the coil?

[the legend]

grey and negative

[the legend]

also check the back of the tach and make sure it is set to 8 cylinders

[dchatagnon]

ok. it works now.
Thanks for the help