If you have IO, and assuming tach’s are correct, you may want to check for a spun hub. If you start throttling up to get on plane and one engine feels like it “breaks free” while the other labors, then the spun gun would be on the higher RPM engine.
I had a similar experience when I purchased my boat. Unfortunately the survey was done lightly loaded and it didn’t slip until the boat was normally loaded for our first weekend. The slipping engine would wind up to normal RPMs and the good prop would labor and the boat would barely get on plane.
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