Seymour Snerd
Lifetime Supporter
It's not too difficult, but not a snap either. The hardest part is getting the old one out; it is retained by the usual post and knurled-nut method, and one of the nuts is on the far side relative to the access panel. Just be prepared to squeeze your hand through some narrow openings with somewhat abrasive fiberglass edges. If either of the nuts is on very hard it can be frustrating and hard on your fingertips.
The new one is retained by a ring nut with the ID of the tach, with very fine plastic threads, so the trick there is holding the nut against the threads squarely enough to get it started. Once started you just spin in on with a finger tip.
I don't recall the antenna cable routing exactly, but it was fairly obvious at the time. Also the cable is far longer than you need so you have to coil the execess up and hide it somewhere, or shorten it if you want to deal with really small coax. Doable but probably not worth it.
Howard's probably right about hiding the antenna. It might be worth a try leaving it inside the dash and/or experimenting by testing it sitting in the passenger footwell to see if it receives a good enough signal through a few layers of bodywork, etc.
The wiring is a little more complicated because you have to include a DC-DC converter module they supply that powers the backlight. But that is something you can deal with "on the bench" ahead of time such that in the end you are down to four wires: ground, ign., bat (to keep the GPS alive for faster fixes), dash-lights. So three of those you can get from the ignition switch, and the fourth is "left over" from the original tach.
(BTW sorry about the odd wording of my question about bouncing. I misread your original post as meaning you had a GPS unit that was bouncing. Most (all?) SPFs come from the factory with the speedo cable severely bent right behind the speedo, and I suspect from that alone are guaranteed to have cable whip and bounce problems, if not infant death.).
