I have a Singer 111W151. When I was researching what machine to get to do my boat's upholstery, I read to look for a Singer 111 or 211 as these are walking foot machines. I have since learned that there are other types in the 111 line. My machine is a needle feed machine, not the recommended walking foot.
I didn't do too badly getting this machine though as I only paid $200 for a fine working machine with the power stand.
It works great when I sew the marine vinyl material face to face since there is a fabric backer. I was having trouble where I tried to face stitch, such as the top stitch on a french seam. The stickiness of the vinyl was causing the material to stick on the presser foot causing messed up seams and stitches.
I tried rubbing a rag that had some food grade silicone that I had laying around along the intended seam line. This worked great and the material went right through with nice stitches. I can't imagine that the silicone would hurt the vinyl but I have a piece sitting with some silicone on it to see if there's any effect. In a production environment this wouldn't be cost effective at all but for my uses it works fine. I am looking to get a Teflon foot which would do the same thing I think.
It only sews slowly now due to the pulley change I made. I wanted to see how slow I could get it to go with what I had on hand. If that didn't work I was going to get a servo motor.