In the APRIL 2019 concern of BOATING on page 65 there is a "BOATING Certified Test" of a Four Winns VISTA 355. The fuel consumption, engine speed, and boat speed data look quite reasonable, but the author of the article, Kevin Falvey, seems a bit confused about basic mathematics. Kevin is also the magazine's Editor-in-Chief, so perhaps no one else looks at his copy before it goes to print. He writes:
The boat's most economical cruising speed comes at 5,000 rpm and 33 mph, where you can net 1.1 mpg. If sea conditions allow, bump it up to 37 mph: you'll only give up one-tenth of 1 percent in efficiency...
With real math, that means that the MPG would decrease from 1.1-MPG to something less by a factor of "one-tenth of 1 percent." We just need to multiply 1.1 by 0.001. That means a decrease of 0.0011. So we would expect the MPG at the higher speed to then be 1.0989 MPG. However, in the table of data, the decrease in MPG is to 1.0 from 1.1, which is a factor of -0.1. To express -0.1 as a percentage of 1.1, we would call it a 9-percent decrease. To call a 9-percent (0.09) decrease a decrease of only 1/10th of 1-percent (0.001) is an error by a factor of 0.09/0.001 or 90-to-1. Expressed as a percentage that is an error of about 900-percent.
When I read published statements expressing mathematical relationships that are in error by a factor of 90-to-1, I have to wonder what else in the accompanying article might be improperly stated.