My original tach (1988) E-28 Universal M10) got fried last year in a lightening strike. Last winter, I went to the local used marine parts facility in Quincy Ma. Found a similar 4000 RPM tach, put power to it, it went to 0000 rpm and seemed OK. Put it in last winter. When I start the boat it seems to read OK. As the motor runs for a few minutes, the tach reads a lower and lower RPM and does not vary from about 800 - 1000 prm no matter what the real engine speed is. There were a couple of plastic adjustable screws on the rear but I never touched them nor do I know what they are for. Any suggestions? PS the alternator was replaced after the lightening hit.
