Re: Tach
You could do a real simple visual test- pull it off to see if any of the non-dialectric gel is pitted underneath.
Mine was intermittent. Once the motor was at peak temp for a while it would start to act up again. I started having all sorts of strange problems after a while as the battery started to drain - not just with the tach, but also engine problems.
I replaced the rectifier - not much better. I put the battery on the charger for a day then took it back out and haven't had an issue since and I've had it out numerous times for a total of about 30+ hours.
Here's my thread on it with excellent information from Joe Reeves.
http://forums.iboats.com/showthread.php?t=552888