Offshoreonly.com - Livorsi tachs acting strange

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - Livorsi tachs acting strange - need help please (https://www.offshoreonly.com/forums/general-q/206252-livorsi-tachs-acting-strange-need-help-please.html)

Quote:

Originally Posted by eichhoma (Post 2860250)

Well, we did more testing this only to leave me even more confused. We found that disconnecting my alternators completely from the system made my tachs work just fine. So we swapped them out with the alternators from my buddies Fountain (same exact alternator/part #) and they still fluttered and fell back towards zero at 3800 RPM!! We also ran a known good tach directly to the coil and it worked fine.
Then we narrowed in on the harness to the alt's and the wiring to the tachs in the dash... ran known good grounds, signal, and power directly to the tachs with no improvement.

I spoke to Livorsi and they suggested I try a couple new tachs, ones with metal cases... mine are plastic. They seem to think it is interference/ radio frequency interference stuff that maybe the better cases might prevent. I think its a reach but bought a couple to try out. They should be here tomorrow. They are working with me so I cant complain. Said they would take them back without the resotckinig fee if they still dont work. The bottom line is the tachs were fine before the engine rebuilds, and the only thing different is the blocks (went from 454's to 502's)... I cant understand what could be different now that someohow some freak signal is being sent out to interfere with the tachs??? The alternators have me very curious.... but the wires going to them are all good.

Any other suggestions? Much appreicated fellas.

I had the same problem as you last year. Pulled motors to freshen and then re installed and tachs were bouncing after 3500. I called Livorsi and they sent me two filters to install on the back of my tachs.That didnt work so they sent me two new style tach with filter built in and they worked perfect.They are a couple of hundred rpms off from one to another but at least I can read them now up to 5700...

Anthony

Thanks Anthony.... I have a couple on the way from Livorsi and am going to try them out this weekend.... SInce you were in the same situation, I still cant help but wonder what is different... somethign obviously changed or was connected differently than before the motors were pulled.... Thanks! I will let you know the results with the new tachs. Mark

Hey Was That The Correct Cable End.

Quote:

Originally Posted by Wobble (Post 2860352)

That is a good idea. also is there any chance that you went from a resister type spark plug to a non resister? I am sure that you are not running the same plugs if you went from NA to blown

http://www.ngk.com/sparkplug411.asp?...esistor&mfid=1

Just found out the plugs are MR 42 t's.... says they are resisitor plugs....

Quote:

Originally Posted by johnnyboatman (Post 2860865)

Hey Was That The Correct Cable End.

It sure was, thank you VERY MUCH!!!!

did you get it fixed?

Did you ever fix your tachs? Was it the plugs?

I did a motor swap this winter as well went from 496's to 500efi's and now my starboard tach is doing the same thing. Jumps around after 3000. It's really bad up around 5000

Cure for Livorsi Tach Problem

Please see my post (#12) in this thread:

http://www.offshoreonly.com/forums/g...500-efi-2.html

Sorry to bring back such an old thread....

I am having this same issue. Tachs work great at idle....once rpm goes above 2000 they basically go back to zero. I grounded the distributor cap hold down screw today. No help. Any ideas??

1997 fountain fever 38
Twin 540s that made 750hp

Quote:

Originally Posted by wybmabiity (Post 3150930)

Please see my post (#12) in this thread:

http://www.offshoreonly.com/forums/g...500-efi-2.html