In article 382821_38f97650c033df6f665c61c9902cff2d@boatingfo rumz.com,
says...
hello everyone! I am new here and I have a quick question about
tachometers. I have a boat tachometer that I am trying to hook up and
test but it isn=3Ft the normal 12v, ground, and signal similar to
vehicles. I was hoping someone here could provide me on some insight
on how these work. I greatly appreciate any help.

Here is a link to the rear of the tach.
http://www.flickr.com/photos/20166103@N05/2761111888/
[editor: picture validated as of date of this post]

Thanks,
Mark



If the tach reads RPM from a tap on the alternator then there will be
three connections to the instrument. Plus, Neg. and input or signal
which is the connection to the alternator.

--
Cheers,

Bruce in Bangkok