PerfectPass...Easy Install
I installed PP Stargazer last year in my '06 Outback. I had Moomba Cruise prior to that. I talked to Gary at PP and we determined that I needed the install kit. It took some time to figure it out (about a day), mostly because I didn't want to mess up my $30,000 ski boat, but looking back at it, it wasn't too bad. There was some minor electrical work I had to do to the ECM module plug ( I needed to add some jacks to the plug that would allow PP to "hijack" the ECM signal so it could tell the ECM what to do), run the cable from the module to the ECM Plug, pull out the old speedo, put in the new one, plug it into the module, and plug in the GPS antenna and speedo wheel. The two hardest parts of the process was working the plug, finding a place to mount the module that would keep it fairly dry, and finding a way to power the system-I ended up hooking it to the old Moomba cruise power wire-for some reason it would only work that way.
Talk to Gary at PP-he'll be able to tell exactly what you need.
Also, for the speed issue, if you're not running it off of GPS, the paddle wheel under the boat may be jammed up, causing inaccurate speed readings. just a thought-my old speedo didn't work at all for the two weeks I got to use my baby this summer.
Sean