Well I would think they (Baja) and other boat builders buy speedos and other gauges in bulk like everything else so they buy 100 MPH then if you get big power say a pair of 900 hp motors then it might do close to 100 MPH.

Mine is a Gafrig Livorsi and is inacurate by 0.5 mph... Witch is the best I have ever seen.

However, my pre-boat add a Faria gauge and was off 5-7 mph...

Go figure... ?

I also have the monster Gaffrigs on my 25 and every time I get the handheld GPS out I wonder why I bothered! How can a gauge be so accurate? I have to say that ALL of the monster gauges seem to be that good. Trim gauge is perfect. No needle bounce or even a flicker from any of the others. Absolutely the business!
However, you are so right - these 100 mph speedos where you are not even halfway through at 67 are really frustrating. Time for a blue motor

My monster gauges have ussally been pretty damn close.
Liquid