Here I am trying to find out where I should put the engine to keep the COG right. I just put a piece of PVC pipe under the center of the hovercraft and went from there.

Here is a close up of the engine, its a 5Hp briggs. (Thanks Dave)

Here is the mount mostly made and screwed together.

Here I have the mount completly made and I'm test fitting the engine. All I need to do is glue it together and fiberglas the seams.

The other side.

Now I have the mount glass and mounted to the hull, and I also have the engine mounted to it.

Next I made a couple support fins for the duct to keep the prop centered with the duct.

I attached them to the mount with an aluminium braket that I made.

Then they are glued and fiberglassed into the duct. You can also see a couple of the hard points I put in for the guard.