I Don't Trust My Tach.
 

Hi, I either gained 200rpm some were, or my tachometer is on the fritz.
My boat is a 1997 24' Superboat with a 1999 7.4MPI and Quicksilver gages.
I went for a ride yesterday and my tachometer was reading 4600-4700rpm at WOT. For the first part of the season, I have been maxing out at 4400-4500rpm. My speedo was not working, but I don't think I was going faster.
At on idle, the tach. was reading 600 like it has all year.
Is there a way to check the tachometer without changing to out. Can I wire another in parallel and compare.