water pressure question

[johnmcmanus]

HI , I am new to the form so I appoligise if this question has already been delt with.
That said here is my question, the previous owner removed the thermostats in my Evinrude 150 Hp possible to make it run cooler, I found that the impeller was toasted. My water pressure guage marely moves and hangs between 3 to 5. what should the pressure be and what might cause the problem if there is one, maby the missing thermostats?
Also what should the heat range be for a 1993 Evinrude 150 Hp. I believe that my temp sensoes in the heads close at about 170 deg.