You can find them in the inboard motors on many not-so-old boats. My 10 year old Mercruiser uses one (although I think the newer Mercruisers have all shifted to EFI). I found the site to be very instructive. I'm always interested in learning more about how the engine in my boat works in case there's anything I can repair at home instead of taking it to the shop. I think a lot of the information on the site is transferable seeing as how mine is essentially a GM produced 'car-engine' mounted in a hull (minus a transmission and some other things).