SB The motor was bored 030" over.

NPerfect statement if you pushing more torque and horsepower or if your bouncing off the chip only then would I increase pitch of the SAME style and brand of my best prop. Labbed or not. For instance I increased my hp by 100hp per motor. So I went from stock 28 bravos to 30 labbed bravos. Turns out at this point in testing I made the right choice since I still plain out at 2000rps and I'm running 45 mph at 2900 no trim.... Man I can't wait till I break these motors in this weekend for final oil change and see what see will do. But it is probably all in the prop for you.

Rev limiters should be NOT used as a top speed limiter. This is what a prop is for.

They should be used to protect the engine from too high a free rev if issues happen.

BTW, I have a sweet labbed 26 hydromotive right hand for sale $350 shipped

Perhaps the newer motor doesn't like the old gas in the tank? If it ran fine on the dyno the odds are good that it's a simple linkage out of adjustment or pissed off fuel pump that didn't like sitting for a few months. Best of luck!

I think others have touched on the need to make sure you are getting adequate fuel to the engine. Have a buddy ride along to peek at the fuel pressure gauge while you give it gas to make sure that you are not dropping pressure under load. It's possible that your pump is getting tired and not keeping up with the increased demands of the new engine. I encountered similar issues - built a 489 that produced 585 HP / 605 ft/lbs on the dyno, and then could not get the RPM's I should be getting in the boat. Determined that my fuel supply system was not up to the task. I'm in the process of addressing that right now.

^^^ agreed. Check fuel pressure

Great input here for sure... I don't know about the 5 blade props but how are your mid range numbers? Better or worse than with the old prop? I understand you gain efficiency in the mid rpm range but top end may suffer a bit? I built a 502 for my 26ZX and I tried to copy the HP 500 engine. I ran a best of 70 at 4950rpm on a 93*day. Cruise was excellent at 3,500 rpm giving me 50mph in ideal conditions...... I am using a 26P 4blade Bravo1.... It does not cavitate or blow out and gets on plane easily....... We have similar size boats and my drive seems to sit very deep in the water........ Definitely make sure you are not running lean as it would be a tragedy to hurt your new motor. I am using a wide band AFR gauge to tune my carb and it has been a huge help and piece of mind knowing exactly where my carb is at.......

I would also put your old prop back on and see where you stand....... You have a known baseline top speed so you can compare apples to apples........

Reputable marine shop or reputable make the 72 nova haul butt shop?