Re: Upholstery help
As an upholsterer, I can tell you that any "patch work" will look exactly like that...patchwork.
I'm unable to tell the size of the cushion by the pics, but if it's a jumpseat, I'm assuming it's in the 18"x18" - 22"x22" range. With standard white marine vinyl and reusing the hidem that is stapled to the bottom, you can get it totally recovered in the neighborhood of $50-$75.
Just get it fixed the proper way. You'll be happier in the long run. While you're there, have them put 1" white webbing on the bottom with a snap in the boat to keep it from flying out again.