I have a 1994 Opti 200 on my Ranger 195. It has about 400 hours on it without a single problem. This morning while running at what I know to be 4,500 Rpms based on experience, I noticed the dashboard tach said 6,000. I then noticed the tach was bouncing all over from 4,000 to 6,500 RPMs, with no change in speed or sound. The motor is running steady, but the tach is wigging out. Can tachs malfunction? Any suggestions? Thanks!