Mac, I'm sure that plate works great, but there are 2 distinct advantages that the hussle plate has over one like yours.
1) First and foremost, you don't have to put it up and down (unless you want to modify it - I did mine so it would be up when I was just cruising). This is important for morons like me. You know good and well you are going to get excited and take off with that thing in the down position. That's either going to mess up your lower unit or shear a pin (if the thing has a pin). That just seems like a pain to me?!
2) The hussle plate has a hole in the middle - bet you are wondering why? Well, you'll find out when you put her in reverse. The hole lets the motor function better in reverse.
MJ, here is where I ordered mine. They have 3 sizes for different HP motors. I don't see anything about Yamaha, so you might want to call the guy on the 800 # to ask. Mine was a Johnson.
http://www.johnsonmarinesupply.com/h...ing_plates.htm