tach wiring

[chrisloveskaos]

i have a 1987 johnson 140 , it did not have a tach so i gto one and reading on these forums here learned how to wire, but i have a problem.
when my motors is idling tach reads 2000 rpm , i know that's not right..
and when i give it gas tach goes backwards to 0.
i have the grey wire from motor harness to s,
black ground from harness to g,
and purple from ignition to p ...
what am i missing, tried 2nd tach same results..thx in advanced..

another ? the boat is a 73-74 wellcraft 16.5 ft center console and has a 30 gallon aluminum tank under the console..should i junk it and go with a new plastic tank in same location?
it needs a fuel sending unit in this one.

 

[bktheking]

Re: tach wiring

Has the tach got a setting switch on the back? Should be set to 6p, sounds like it's not. Have your verified that the charging system is functioning?

 

[chrisloveskaos]

Re: tach wiring

it does and it is set on 6p , charging system seems fine never had a dead battery so im assuming its good.been fooling with it and im now reading the right rpm but it is still going backwards when giving gas

 

[Barnacle_Bill]

Re: tach wiring

test your rectifier