HP is a silly thing to rate a backhoe by. The backhoe runs off of hydraulics. You can calculate how much HP it takes to make X gpm @ X psi and i think youd find that basically any small backhoe takes no more than 6hp to hydraulically operate.
I think what the hp number is getting at, is it’s a stand in for tractor ‘size’. There are a couple reasons a tractor needs to be a certain size to run a backhoe. First one is, just like a 3pt implement, will a tractor do a wheelie just trying to move with this thing hanging off the back? If this thing weighs 1000lbs and you know you can pick up 1000+ on the 3pt and still actually get somewhere, you’re good.
The other thing is what happens when you push on the ground with the hoe? On an extremely light tractor, you can barely push on the ground at all before you just push the back of the tractor up into the air rather than pushing the bucket into the ground. That creates some safety issues, but dealing with safety issues is basically the definition of being an equipment operator, and you can ‘work around it’. Adding weight to the back of your tractor in the form of tire fill and wheel weights will make the backhoe less finicky to operate, but good technique can do more than adding all the weight in the world. One thing you can do to improve the situation is use the loader bucket to push the front tires off the ground. That way, in order for the hoe to pick up the back of the tractor it has to lift the weight of the WHOLE tractor.
I wouldn’t hesitate, personally. Any backhoe is better than none but having the additional reach of the 7.5ft model is very desirable from my experience running a 5.5ft, a 6.5ft and a much larger mini excavator that probably had a 12-14 ft dig depth. The reach allows you to set the ‘spoils’ in more places or further from the hole, AND requires moving the machine less often when trenching.
