Anyone have any experience with a Mach 4 blade?
Anyone know anything about them?

How would you compare them to a B1 or Mir+?

You don't hear too much about Mach props these days and I'm not sure if they're even mfg'd anymore. I believe they were a very respectable prop in their day though. I've never tried them personally, but looked into them at one point. I'm sure somebody that knows will chine in soon.

Ive never heard anything good. Remember you get what you pay for. Cheap props are just that. If you can try it before buying go for it. Ive learned the hard way but still always looking for a deal.

They have been out for years. I tried one once and was quite impressed with it. It was the only round ear prop that could plane my boat off. In fact, the prop was a ROCKET out of the hole! Definetly could ski behind it. The problem is that around 30mph the prop started to slip like crazy and had no top end. I too have heard from several sources that they never were a very good prop.

They work well on some outboard applications.

Cord's explanation is what most of my findings have been. Good hole shot with poor upper end efficiency.