Hi all.
Its been a long time since I have been on the board. I joined back in 2000 but got lazy a few years back!
Anyways, I have a bit of a dilemma.
I installed some Gaffrig gauges in a 1997 Mirage 217. The boat has a 502 mag with Thunderbolt V ignition. Everything works fine except the tach. It reads erratic and inaccurate up to 3000 rpm and then the needle drops to zero.
I have tried the following to try and remedy the problem;
ran a new wir direct from the coil to the tach. Ran a new ground wire direct from battery to tach and tried a new MSD coil. No difference inn the erratic tach readings on any of these mods. I then sent the tach back to Gaffrig and they checked it out. mike himself checked it out and informs me that the tach is all OK. He remembered someone else having a problem with one of his tachs and thunderbolt V ignition, but he couldn't remeber the solution.
Any ideas?

Thanks

I went through this recently..... a couple months ago and spent hours on the phone with Livorsi techs....

check engine grounds, ensure the module AND the bracket for the module is grounded. I swapped tachs to a better series that had a metal case and built in filters, and they worked fine. My old tachs were fine too, but there was interference being picked up that the better tachs filtered out. Hope that helps.

You mean the module on the distributor?
OK, I'll check that

Thanks