Don't know about the water pressure gauge/sensor. I just put a temp gauge on my 73 Merc 500e, putting the sensor on one of the head bolts. Works fine...all i have to do is glance at the dash for instant temp readout. Couldn't find a tach that would plug into my Mercontrol, so i went with tinytach for $35. Works great. they are at www.tinytach.com
