I resently purchased a H27 sailboat and I'am working on fixing some of the things that are in need of repair. I will be pulling the boat out of the water to replace some of the seacocks and I need to replaced the knot meter "I Think". What has me confused is..laying next to the knot meter that goe's through the hull theres a knot meter laying next to it with the line attached to the top of it. But the one that is currently placed through the hull has no line at all, and theres no place to attach a line to it, but it doe's have a small clear round top and it looks like theres a fuse or metal object in it.... The un-attached meter is presently hooked up to display box or unit that reads out the water temp and depth and supposed to read out the speed, well thats obviously not going to work just laying there. What I'm wondering is, do they make a knot meter that does'nt require a line attached to display unit. I asked the previous owner of two years ownership and he didn't know and when asked if the knot meter worked he said he thought it did "???" OK,..If they do make a knot meter that works with some sort of electronic signal then I must be missing that part of the unit. I hope I'am making sense?? Anyway I would appreciate any advice.