In the early/mid 70s my dad worked for Berkeley Pump Co. as a PR tech rep to the boat manufacturers in the SE. (basically he went to the factories and showed them how to put in jet pumps) I wish I could remember the stuff he told me about the testing they did at Hallman and Moody on engines. I wasn’t old enough to drive yet but knew a 351w wasn’t the same as a 351C. I do remember that a lot of the engines that people bragged on for cars didn’t have what it took to run in a jet boat.