trim tilt gauge hows it fitted

[Dino89]

Hope this is the right forum i have a 1999 mercury 50 on 1990 avon 4m searider and with power tilt trim would like a gauge so i know where its at
how do they work and how do i fit one any advise appreciated no absolutely nothing about them so idiots guide would be good
also cheapest place to get one

[Tim M]

You may well have to fit a trim sensor on the engine as well as the gauge to your console....