Whacky tachometer

[Odayssea]

My starboard tachometer has tended to run run about 10% faster than my port tachometer. I am guessing this is a tachometer problem and that the tach is not showing the real engine speed because it does this when the the engines are perfectly synched and when the throttle is about the same. Also, the starboard tach is more erratic, often jumping around a bit, but it is never slower than the port tach when they are synched (sometimes the same but usually 10-15% faster). This past week it was wunning closer to 25% faster (cruising at 3,200 on the port engine but the starboard was reading 4,000). With the difference increasing it is making me think it is time to change the tach, especially since I am now getting a fast whirring sound from my instrument cluster, which may or may not be related to the Questions: does this make sense? Should the tach be replaced or could it just be a wiring problem? Your suggestions are helpful!

 

[Lazy Daze]

On the back of the tach is a little switch. Try "exercising" it a little - then make sure it is put back to the "8" position for a V-8. I'm not sure about the whirring sound.

 

[twomad]

I had the same problem with 1 of my tachs and i did exactly what lazy days said to do. I saw it talk about last week on this forum. Did it this weekend and tach is fixed saved a lot of time and effort trying to figure it out. This forum has saved me lots of time and money, thanks to all who help

 

[Plane 2 Sea]

+2 on our '96 330 SunDancer