I have a Universal M25 in my O'Day 35 that runs like a top, but the tach fluctuates almost all the time, usually in the general vicinity of the actual rpm (I think). The alternator and regulator appear to work well with each other and I replaced most of the main battery wiring recently with no change. The rest of the wiring could use a good going over, but would anyone have an idea where to start specific to the tach?