Tacho issues - how do I diagnose/replace?

[rcon]

Where do I start learning about tachos for carb'd engines? Port wanders all over the place, and this is attached to a brandspankingnew 4.3l TKS mercruiser. Starboardis a little better, but also wanders and often sits about 200-300 RPM higher than it should.

First thing I plan on doing is swapping the connections to the gauges to see if the problems follow the gauges or they're elsewhere.

Next up, and this is where I think this is going, I plan on replacing the sender units. Problem. What the heck is this "sender unit"? Is this a DIY job or something for an auto-electrician? is there a site someone can point me toward for generic replacements?

Is there some tool I can hook up to see what is going on?


Oh for EFI

 

[Xplicitlnck]

Don't do anything. I had thr same problem. Did a little research and what I found was this. Pull the bezel that the tach is attached to. Do not remove it no need to. There is a selector switch on the back of the tach. Use a flat head screwdriver and turn it a couple times to clean the contacts. I turn mine about 15 times. Reinstall and for once enjoy an easy and free fix. My rpm tachs would jump all over the place. I did this and no problems since. The contacts on the switch get a little corroded and cause a bad connection. Hope this solves your problem

 

[rcon]

Now that idea i like.

I'll report back for posterity

Cheers.

 

[Air O'Nautical]

Should do the trick, an easy fix for once.
Make sure to note the original position of the selector to reset it.
Resist the temptation to spray any contact type cleaner in there...it can damage the dial and will look horrible while running at night.
Don't ask how I know but, "Flounder Pounder Marine" probably has a replacement for you to.

Cheers,
Mark.

 

[Xplicitlnck]

Any luck?

 

[rcon]

Not yet. Season has really turned over here. I'm heading down this coming weekend tho.

Will post results.