I use a size 14 needle, and If you can get a roll of cash register paper, or adding machine paper, you can set the roll in your lap and let it unroll as you sew over it.
Also, lengthen your stitch as long as possible, and use nylon upholstery thread on top and in the bobbin.
If you can't get the C R paper, you can cut strips of paper, and just keep adding them as you sew.
anyone else want to share their knowledge sewing on this Marine vinyl
Use a 90 sharp needle and if you have one, a teflon foot. This foot has a coating that allows it to glide on the vinyl and not get stuck. If you don't have one try using some either tear away or wash away stabilizer to keep it from sticking. Good luck. Hugs. Nan W