Re: 1996 Force 75 on Bayliner 1704
1st check, there is a small hole in the front of the lower unit check and see if it is clogged that is the most common problem. If that doesn't work go to the back of the speedometer pull the hose off and take a air blower to it, see if you get a reading. If all that works check the air line from the gauge to the motor to make sure no leaks.