25 Sportdeck chine walking
 

Ran my boat last week after getting the Imco steering installed. 32" Bravos spinning out on Torquemaster lowers. 20" Optis on lowest mounting hole. The boat starts to chine walk around the 70 mph mark. I was able to get it to 79 GPS using the K-planes to stabilize it which obviously adds drag, reducing top speed. I have read these hulls can get sketchy in the upper 80s but not around 70. I have checked the last 4' of the hull with a straight edge and it is true. My steering is tight. I don't know what else to look at....[ATTACH=CONFIG]547741[/ATTACH]

where is your prop shaft in relation to the bottom of hull? If it is high enough and with a 32 pitch prop it is creating quit a bit of lift on the transom which it is trying to lift it out of the water and then falling side to side so to speak.
You may want to try a jack plate or an engine bracket

you need to raise them up. Ed here on the board will be able to help

Prop shafts are just below the running surface. I would have to measure to give exact height in relation to the transom. The props have the diffusers cut off to help eliminate stern lift as they had been used on my 28 Skater.

someone mentioned to raise the engines, you can try it, it is easy enough but I do not think going up will correct it. and ya may not be able to get on plane.
I have been dealing with I/o drive height issue all summer. propshaft level with the bottom unable to get on plain. 1 inch spacer can get on plane with a non polished prop and ran best speed of 87mph that I saw once, with a 5 blade. and would chine walk.
2 inch spacer ran 87mph every time I tried to run wot. and chine walk went away.

34 pitch is quite large for that size boat so it wants to lift the transom out of the water.. you may want experiment with props 3 blades do not give you as much transom lift but they also don't make them that large. you will probably want something that is made for for bow lift. or change gear ratio

try raising the motors first. Wont cost anything. One of my boats is a 22 velocity. I kept raising the motor and kept getting easier to drive. To the point that I had to put transom mounted water pick ups on the boat. I am now about a inch and a half above the bottom. I am running twin 260s with no k-planes and its a hand full. Keep driving the boat and get some good seat time by your self in the boat and you will get the hang of driving the chine walk, and figure out how to balance the boat on the gear cases

mine with 2.5's were 1" below

My first performance boat was a 2004 22 Velocity with a 300X. It was definitely a drivers boat and took some seat time to learn. Maybe I lost those skills after running a Skater for the last 8 years!

I believe this is a padded boat
so at 70+ hull is trying to get on the pad
just as described above if gearcases are trying to lift the transom above the pad as speed increases chine walk gets worse
O/B boats are set up differently to bottom and not have slip getting on a plane like an I/O
also if trying to make a fast boat vsing a good handling boat the set ups are different
for higher speeds got to find the gearcase happy spot to where its using the gearcases as a pad
so nosecones or a sportmaster helps
the higher the centerline is the less it lifts transom on the surface at high speeds
and learning to drive a padded boat is a factor
so seat time and motor height are big factors for high speed O/Bs

So essentially raise the motors or possibly try different props that do not give as much stern lift as Bravos...?