Tach problems, Any help would be appreciated . Tha

[bertsboat]

Any help would be appreciated
My Tachometers bounce up when they hit 3000 RPM's.
I have seen this before on another boat I had but don't remember the remedy.
They are old school BBC with regular distributors and coils, not electronic ignition.
Any suggestions?
My thought is that the alternators may be spiking the system, but what do I know?
Thanks in advance,
Bert

[MOP]

Most of the time grounds are the culprit! Your thought may be correct, keep an eye on the volt meter if it jumps @ 3K then you could be right.