Tachometer electronics help...

Hello I'm new to the forum and I am really hoping that you can help me. I've asked this question on another site and was unable to get any kind of help. I have a tachometer that I am trying to repair but it is a little different that other types of tachometers. It doesn't take the normal +12v/Gnd/Signal. I've heard these boat tachometers work a little different than vehicle tachometers. If there is any information that you can give me I would greatly appreciate it. Here is a link to some photos of the tach.


https://www.flickr.com/photos/20166103@N05/sets/72157606877440549/

Thank you for help in advance. I really can use any help that you can give.

Sorry, bad link.

Boncuk

Yep, bad link here to. First what is the mfg/model number of the tach that you have?

I edited the link above. It should work now. Thanks to the both of you for responding even though my link was bad. I was looking at the circuit board this morning and there are 3 actual inputs BUT only two are fuctional. If you see the picture there are three prongs I guess you can call them but two prongs actually are connected to the circuit. I don't think the tachometer is being grounded by the case like some older electronics are. So I don't think this tach uses the normal 12v/GNd/Sig. I spoke to the guy who asked me to look at this and he told me it only uses signal and ground. *shrug* I've never seen anything like that before. As far the mauf. of the tach it say: Sun Electric Corp. Chicago, ILL. I hope someone can give me some insight I'm completely stumped.
Thanks again!