"Okay so why didn't Islamic (Moorish?) ships come over sometime around Colummbus? "

Moorish ships at that period were galleys- powered by sail when conditions were right, but mostly by oar. They didn't use the dhows of the Indian ocean (even there, trade was normally by coastwise hops). They had to be long (so you can get enough rowing manpower on board), low in the water (so the rowers can reach without the oars being too long and heavy), slender and shallow (so they aren't too heavy for the rowers to move), and you had to feed and water the rowers (you can't afford your power plant to break down mid- voyage), and that means the bigger the power unit, the bigger the fuel bunkers. In addition, they were shell- built which was excellent to keep down the weight, but not good for oceangoing strength in a big vessel, and has a definite limit on size.

Note that they don't benefit from what Brunel realised at the start of the iron ship age- that if you scale up the ship, the volume goes up by the cube of the scale, whereas the drag only goes up be the square, because they can't scale width and depth as well as length because of the oar power.

Sail powered ships have a different, smaller problem - they mass is cubed, but the sail area only squared- reducing agility and manoeuvrability. This was mitigated (much later than C's time) by adding more masts and more sails on each mast, culminating in the clippers and the three skysail yarder bound south round the Horn. The framed ship could be made strong enough to take it.

So it's the same old same old, a conflict between the construction technology and the power requirements. And that's assuming the Moors ever thought it desirable to go there.