Livorsi tachs acting strange - need help please
 

So, I just had new motors put in my cig. Went from the stock 525sc's (which were 454 blocks) and went to 502 blocks and running TBS blowers at 5 lbs of boost. I am in my break in period right now and I noticed that once the tachs reach 3800-3900 rpm's, they start fluttering and freaking out; actrually going backwards. Its not the motors - they sound and run great. Does this sound like an electrical issue? Ground maybe? I am kind of stumped. The tacjs worked fine before the rebuilds, but now, they work up to 3800 and freak out. What should I be looking at? modules? wiring? grounds? The GPS speedo also does not work. Any feedback or thoughts would be much appreciated. Mark

I would have to guess its in the wiring. Did reuse the TB IV's or go with new ignitions??????

Stayed with the TB IV's and have the v6m modules.... I was kind of assuming it has to be wiring too, both worked just fine when the boat was brought in for the rebuilds. I just dont know if they share a ground or what is going on up under the panel. any suggestions?

I have heard that is due to slight moisture in the gauge itself.

Would that stand to say they could dry out and the problem would go away? Or should I send these to Livorsi to be tested? It just seems strange the problem appeared right when engines where swapped and they worked just fine. The boat never sat outside, or got wet this winter. And with the gps speedo not working as well (both worked fine when boat was brought into shop) It just seemed to me that it might be related to wiring..... any other suggestions? I really appreciate the feedback.

I think you have a bad ground or loose sender wire somewhere. Pull the plug on the wiring harness by the engine and spread the prongs and clean if needed. Check for loose ground straps or even not connected wires on the engine. I say this because you just installed the engines and now you have problems. I doubt you have gauge issues. The engine can run fine but if the ground to the dash is not hooked up or loose...

Check the grounds on the modules. They have a black ground wire and the module case/mounting plate also needs to be grounded.