Roughly 300hour 502 Mag MPI's Bravo 1 drives, four bladed SS 28P props.

What GPS speed should I be seeing at WOT and trimmed out?

Thanks

Boxes? Conditions? People? Fuel? AC? Water? A lot of contributing factors to top end.

No boxes, flat conditions, myself (175) boat girl (119) :-), quarter tank, factory AC, water tank full.
Boat new to me, max has been 51.5 GPS. Something's gotta be off.

Def not 50.

Low to mid 70s. 502s are only rated 415hp they are heavy SOBs too. the Merc 500s have 470 and top end is 75-80s on them. 525s have heard 83 in perfect conditions half fuel half water two people tail wind etc etc. whats the fascination with WOT?

Only real way to know is to drop the hammer and find out.

Full throttle, trimmed with the conditions I've stated, I've only seen 51.5 GPS max. Suggestions?

What RPM are the motors running?

67-72 on gps depending on load and conditions and all... you are way off!

TRim it out, bring tabs up.... OR...... fix whats wrong with it....that's a cruise speed not WOT....

Sounds like a timing issue or fuel restriction

If your trimmed out properly boat should do low 70s. Trimmed out should be no tabs and 3-5 on your drives. What about maintenance to fuel filters, water seperators, and plugs? Are you running marine fuel versus ethanol pump gas?