Bruce in Bangkok wrote in
:

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.


That must be it. It only goes up to 4000 RPM so it must be for a diesel.