Ive installed quite a few of these and have not seen this problem. It sounds like the hose run issue allowing air into the system, especially as you mentioned the problem stops when you raise the hose.
When the
bilge pump is operating but no
water is being discharged this is typically caused by an air lock. An air lock occurs when air is trapped in the impeller chamber; centrifugal pumps by nature will only move
water (not air) and do not have the ability to self-prime. Air can trap in the discharge hose if the
installation is over plumbed and angled. A dip or drop in the discharge hose can create an air lock which will prevent the
pump moving water but it will keep the
motor going.
Since you say it works when you move the hose then I suspect repositioning the discharge hose for a short vertical discharge might do the trick. Install
pump below water line to insure sufficient water flow. Other possible problems are the Pump strainer and impeller area can be clogged with debris but yours is new so seems doubtful. Another trick is to make sure the float switch/ sensors are facing aft to that normal slosh won't trigger them unnecessarily. I make a 1/4 inch
epoxy wetted
wood plate and put the pump and switch on it, and seat that to the
bilge as a system to keep it a bit above the
bilge. Good luck