Need help with Suzuki trim gauge

[suzukiDT55]

I have a 1987 DT55 that I need to hook up a trim gauge to. It has the 2 wire sender light blue(up) pink(down).I orderd this gauge http://www.boats.net/parts/detail/suzuki/S-99105-80005.html which states it for a 2 wire sender for Suzuki but when I received today there only one post on the back of the gauge that a sender wire can be hook. Is this the right gauge if so where would the other sender wire go? If the wrong gauge what gauge do I need? If this helps the the gauge has one post for ground-one for + and one for a sender wire.Wiring diagram that came with it says nothing about a 2nd sending wire and only shows one sending wire to hook up.