Hydromotive p5x's
 

2005 35 fountain lightning with 525s with stage 1 whipple tune on ecm. I have 30 pitch hydro p5x's and turning around 5300 rpm. The limiter is at 6000 rpm on the stage 1 tune, should I get them labbed to pick up a few hundred rpm and a mph or leave them alone??

How many hours on the valve springs and recent inspection on the rockers? Reason to ask is spinning additional rpm on weak components is not a good idea. I wouldnt prop for 6,000 once valve train is verified solid. Shoot for 5500 to 5700 which would be a pitch down, in your case 28s or have your props labbed, edges sharpened, and possibly cut down diameter. A prop pro will be able to guide you. A pitch down stock prop would be easier/least expensive of the 2 but not as fast as a custom dialed prop.

What improvement did you see with the whipple changes to the ecm? I am doing the top end refresh on my 525's right now and have thought about the change, just don't know if it's worth the added hassle of finding the higher octane fuel on the water.