I run twin 93 225 Evinrudes. The port engine is on its 2nd tachometer in 18 months, this last one worked ok for a few hours and then began to read low at all throttle positions. I just changed the voltrage regulator but this made no difference and the rpm it shows continues to drop and is way off - problems seems to be gradual deterioration. All connections at the tach are clean and tight. I read somewhere that a bad fuse in the engine could raise resistance and upset a tach but my mechanic does not buy this. My voltage reading is accurate at 17 when running hard but drops to 13 at idle speeds - same reading on both meters I allways run on battery 1 or 2, I use Delco Voyager 27's which apparently draw a lot of voltage - the new regulator did not make any change to the voltage readings which check out with an independent volt meter. Could my old regulator have been destroying tachs, I have not tried a new one since installing the new regulator. <br /><br /><br />Peter
