The transom extension bracket is pretty easy to build if you have an aluminum metal shop in your home area. I had to have one built to put on my jet motor to a 20" transom. Had to raise it over 8" to make it right.

Make sure you silicone all the bolt holes before putting together because they have a good chance of leaking if you don't.

Your boat should run with the jet unit but you are going to lose about 25 to 50% of your speed.
Heavy loads a little more and light loads a little less.

You might have to do a little up and down moving to get it just right. You will know when it is there.

fp