2008 tracker avalanche with 150 optimax trouble planing and porpoising

by OLLY
(Jefferson,MA)

purchased a used 2008 tracker avalanche with mercury 150 optimax engine.prop is ss23 pitch

first time I took it out it had difficulty planing with just me in boat.once on plane top speed is under 30 mph

any attempt to trim up only leads to violent porpoising
Engine won't get above 3500 to 4000 rpm top speed is 25 to 30 mph

put plastic plugs in the prop vent holes, no change
talked to previous owner and he indicated that the boat would do 63 mph and run was very stable.

tournament fishing with a full livewell and another fisherman is an even worse condition.

Any ideas