How much compression would a stock 1997 454 mag mpi have on a gauge, I know they all need to be within about 7% of each other, but what would a stock reading be? should it be over 150?

I believe 140-145 is "normal". A leak down test is more accurate.

Merc manual says 150 psi, I would be happy above 140 psi

Thanks for the reply, a leak down test is best, but this is better than nothing
Mark