It runs well. The engine was balanced to within 4 grams of reciprocating weight when remanufactured in '02. Best performance ever was on a cold day using my old handheld GPS, showing 46 kts, or 53 mph, using the same prop behind a Hydro-Flow nosecone.
I've seen a '78 20' CC reach a true and sustained 53 kts (61 mph)with a 2.5L 200 Merc on a jackplate with a nosecone/low-water pickup from Bob's in Ruskin, turning a 24"P overhub "chopper". Slow out of the hole, though.
And I know the 23' Seavette with twin 260hp 5.7L Mercruisers was capable of 68 mph, and with twin 235 Evinrudes, in '84 a SeaVette I was riding in hit an indicated 73 mph on a CMP/Keller speedo. (Very accurate water pressure speedo)
SeaCrafts can be very fast. They were designed that way.
Yours can be, too.
__________________
Common Sense is learning from your mistakes. Wisdom is learning from the other guy's mistakes.
Fr. Frank says:
Jesus liked fishing, too. He even walked on water to get to the boat!
Currently without a SeaCraft 
(2) Pompano 12' fishing kayaks
'73 Cobia 18' prototype "Casting Skiff", 70hp Mercury