I have a Ferris IS 3200 with the Big Block EFI and 61 deck. I purchased this unit from a private party this spring with about 140 hours on it. It has a noise that starts about 20 minutes into mowing. It is one of those noises that is going to be a bugger to figure out. It is still there with the deck off, so eliminate that. It sounds like the outside edge of a pulley rubbing against something, I thought at first it sounded like maybe the spinning engine screen, but it could be any number of rotating pulleys. If I shut the engine down and let it sit for a couple of minutes it will usually not show up for a few minutes. Once it starts it seems to continue until you stop. It remains at low idle. I have farmed around every type of ag equipment you can think of and am usually pretty good at troubleshooting, but this one puzzles me. Mike