GPS results on my new boat

[CPdream'n]

I just bought a 19 foot California Performance w/ a 468. I got 73.1 MPH on GPS. I had gas filled to the rim (24 gallons) and two people in the boat approx. 400 pounds. The boat has logs on it too. I figure if I was by myself and no fuel it would easily hit 75 MPH. How much speed do you guys think I would gain if I put thru transom Bassett headers on the boat.

[QuickJet]

How much you pick up depends on how stock your engine is. My friends Tahiti picked up 3.2 mph going from stock logs to OVER transom headers on a 450 hp 455. I've seen completely stock 330 hp 454's pick up fractions of that. More power you make (heads, cam, compression, intake etc) the more you'll pick up.