I have a bunch of general purpose trenching to do at my ranch, laying 2-3" water lines and direct burial power distribution lines underground mostly. I will probably dig 2 miles of 6" trench in the next year. Probably don't need anything bigger than 6-8". 4-5' deep is plenty deep. My soil is fairly sandy loam, but with a fair number of hunks of granite ranging in size from a fist to bigger. I have a Case 580N to deal with the larger rocks. It looks like a 45hp class trencher with a 5' boom, something like a Vermeer 4150A or 3550A or a Ditch Witch RT40 or RT45 can be had for around $6k near me (ads asking $7k are common). A 90hp class trencher like a Vermeer 8020or 8550A is more like a $17,500 problem. Not surprisingly, I am attracted to the smaller machine. Any thoughts to share before I go ahead? Thanks!
Doesn't sound like you need a 90 HP. Is there something around 60 HP with a 6' boom so you have a little extra capacity in case of hills, etc.
How about a rental trencher on a high flow skid steer, maybe you could rent for a little and let someone else do the fixing. It just depends on the conditions. i did about 1 mile in a day but only 4 feet deep with high flow john Deere 326D Skidsteer. A Track machine would have been better. You need a machine with 0-100 percent creep to control how fast the auger goes into the dirt. Hope this helps. Was putting in video cable to a cabin. Simon C