WILDFLOWER never had a knotmeter, which I consider fragile, foulable, even dangerous, as they are another thru-hull unless you are towing a Walker Log, like I did in the first SHTP. Current US Sailing Safety Equipment Regs (SER's) 4.13 require a knotmeter, or "distance measuring instrument."
When inspected by the Chief Inspector for a past Hawaii Race on WILDFLOWER, he asked to see my speed measuring device. I gave him an orange that had written on it how to take an orange peel, drop it from the bow, time its passage to the stern, compute the speed, then eat the orange. Chuck shook his head, said that's what he used to do, and passed the "device." Not saying that would be accepted in these days of electronic safety requirements. But worked for me.