I have a 1995 Johnson 115 Fast Strike on my boat and the water pressure gage has never worked and was disconnected when I bought the boat. I would like to install a new gage if thats the problem, but I am not sure how they exactly work. the tube from the motor is there and I re-attached it to the gage but it leaked water all over. My question is -- should there be water in the tube from the motor? Is that how the gage works? Any help is appreciated!