Pak,
If you haven't tested your combo yet, that's a dry installation which says nothing. If you want to dial the sweet transom/engine height to get all the available ponies out of any portable engine you must.
-Have a healthy engine and prop
-Engine trimmed at 90?, perpendicular to water level, usually second, third trim hole out transom.
-Distribute weight evenly on deck, if riding solo move full gas tank up front.
-Go for a wot spin lightly loaded on flat calm no wind water cond.
That LU has a weird design, do you have a sharp one piece close edge between 3 and 2 no matter if rear of edge has those submarine type holes ?
If so, you need to raise or lower engine for water flow to skim right under 3 which is the upper small water deflector plate. That must be height dialed under trial and error, will need a aft spotter to check at which tail height is water flow passing at speed once on plane, provided that the 15 HP has enough punch to plane that 14 footer at good speed.
Once at the sweet height you can tach that engine with an induction tach to see if at least you're at middle to max wot rpm factory stated for that engine, can go from there maximizing prop if needed for best combo performance.
Happy Boating