I repowered with a Beta 14 (13.5 hp). I did not do it myself. The mechanic cost was almost the same amount as the basic engine. If course that included cleaning the fuel tank, a new prop shaft, new prop, etc. There is no way in the world I would under take all that. He had to put is some 2 X 2's or about that size on the original motor mounts to get the pan up high enough. Even with the higher engine mounts there was enough room under the cockpit for everything to fit. I don't know the dimensions of the 16, and am not sure you need an engine that big.
I fugure that the new engine, plus installation is almost the curent price of the boat. Oh Well, the Islander has served us well of 25 plus year (we are the second owner and knew the first owner) and hopefully will continue to do so for may more years.
The one problem is the prop pitch. It is obvious that it is wrong, and everyone's "best guess" is a 16 X 7, but the frist "best guress" was 16 X 10.
Hope this helps qith the installation question.