Mustang 17 Wake Question

We have 2 Mustang 17. One is a 74 with a OMC 225, and the other is a 76 that I just put in a new 350 310hp PCM bobtail. I notice with the same gas amount, same exact prop, same everything, the wake on the 76 is larger and the nose goes higher in the air on takeoff than the 74. What is also weird is the old 302 I had in it prior did the same thing. The old 302 would barely turn a 12X14 Federal. Now, the OMC 225 has a 12X15 Federal and so does the 310 hp 76. They both rev at 4800 rpm WOT. Why such a difference? Same prop, same boats, huge engine difference. I also bought a ACME 12.5 X 15 3 blade and the wake is just as large. Shouldnt the prop be alot more pitch on the 310 hp?? I measured the end of the shafts under the boats and compared to see if one was different. They are both identical. The only thing I didnt check yet is total shaft length and engine placements. All are factory and havent been moved. Any ideas?? It bugs me. Thanks in advance for any ideas/input!!

I'd say weigh the boats. You can use a truck scale, or one of the scales at the recycling center.

BKH

Assuming it's constructed like my 78 American Skier, and many other CC models of this era, the entire boat is foam filled outside of the center bilge area and where the exhaust goes. It's also all foam in the bow back to the bulkhead just forward of the pylon. On mine, the floor was just a couple layers of fiberglass over the foam, and the foam was the actual supporting structure for the floor, with some additional wood so the seats and pylon could be secured. I removed 18 or so bags of water saturated foam and each weighed 20# or so. After pulling the carpet, I could see that the floor 'glass was separated from the hullsides, so water just ran right into it (it was also neglected when I bought it, so I expected the worst.)

Is the strut the same distance from the back on both boats?