I can't believe that so many people have got soooo wound up over such a fundamentally flawed article.
Ok some of the data quoted is wrong but putting the engines on to the boats was where it all went wrong!!!
If you wanted better (not correct as you will never ever get this) then the engines need the same variables and same readings to be taken at the same time, place and using the same method.
The sea state, temp, salinty, weight, wind etc, etc were all different. Some to a large degree some to a tiny degree. Add all the variables up and a large differences in the performance will start to appear.
You cannot get fair results in such a test. Only if a bench set up was available with controlable variables would you get a half decent set of results
(PS Flowmeters never ever ever ever accurate!)