I would be happy hitting 80+ MPH, at lease for a while.
Do you know if they are spinning in or out?

I have SSMIII's so I cant help with speed, but just as an fyi you have 260 gallon fuel capacity, 130 per side.

I have a 1990 top gun with custom 454's with 177 blower, about 550 Dyno HP, I hit 72 once but 70 all time in choppy water, but 68 in calm water.
I have 5PX Hydromotive 25p labbed.

Would be happy to hit 80 one day with that boat also...!!!

Im running 23 pitch quicksilver torrent 3 blades turning 5300 at 68 gps in flat water if it helps. I was running 25 pitch 3 blades and could only turn 4900 rpm. I have outboard props on my boat and it really lifted it out of the water at w.o.t. it feels like a 26 foot boat. When I run the 25 picth mirage props it feels like a 40 foot boat glued to the water. They guy tells me it is the cheepest way to get me with in a few miles per hour with out spending the money on labbed props. Ask for Bill Sr. 800-338-8900 Prop shop. He will blow you away with his info I think he has 100 years experiance in props. I have a 38 flat deck with 600 H.P. 468 Tall deck roller motors Dyno at 600 H.P. a peice. Bill is located in Algonac Michigan right by Sunsation

Was getting solid 80 mph w/600's kevlar hull, cover girl cabin.:drink: Boat was a 97

Put it on a trailer get the tow vehicle up to 80MPH and take a picture of the speedo. Problem Solved

I have no trailer Lol !!!

No I mean with some more power for sure (but how much...)

92 gun
 

700's bravo 4 blades merc labbed 28" with extra cup 1" short drives 5400rpm's light on fuel not alot of trim 78mph. i think i can almst turn a hair bigger prop

Those 5 blades are costing you speed because they lift the transom up. You need 4 blades set up for bow lift. I have been down this road before.