Is this water pressure good-1987 Johnson 140

1987 Johnson M# J140TLCUA S# G 7455465
I have about 3psi at idle in gear 5psi idle in neutral 10psi at 4500rpm and 15psi at 5500rpm with prop shaft at 3 1/2inch below pad, had the same psi at 5 1/2inch below pad. Are these pressures good or should they be more ?

Also can these motors handle 5700 to 6000rpm or just stay 5500 to 5600rpm ?

Thanks in advance.

Sounds about 5lbs low, could be the guage.