Merlin,
What props are you running?
What RPM are your engines turning at?
Turning props in or out?

My 84 also has the pad and notched transom.
I am running worked 330 HP 454s making probably 410 HP.
TRS with the Merc transmissions (originally a small block boat).
Props:
Mirage 25 I can get 70.0 MPH on GPS at 5100 RPM
Bravo1 4blade 26 pitch 67 MPH around 4500-4600 RPM
Thanks,
DS

Merlin Post some pictures of the 27 when you get a chance