You aee akiong questionz which require guesses as answeres. Get a $15 gauge and test your boom pressure. That is a simple, fast, cheap, and unambiquous measure of performance. Based in that result we can provide a much better answer.
Dan
Stop guessing. Put a $15 hydraulic pressure gauge on the lift circuit work port and see what your pressure at the work port is.
Do you have any quick connects on the boom hoses?
Dan
Hydraulic fittings have high quality NPTF/NPSF ("Dryseal") pipe threads.
Iron pipe fittings are NPT and often low quality.
The more times you assemble/dissassemble a NPT(x) joint the more deformation and potential for leaks you introduce.
For best results get rid of as many NPT connections...
I seriously doubt 15HP will power that mower in anything but short lawn length grass. I had a 72" rear discharge on a B7200DT and that was full throttle 2nd gear in 6" grass. For reference thats creeper speed.
Dan
You are still a little confused.
When both valves are in neutral ALL flow is going through fhe power beyond circuit and nothing is goung out either tank port. That is the continuous flow (neutral) circuit.
When the AUX valve is operated the PB flow stops, the incoming oil is sent to the...
That will be fine but lets be clear about the line in question.
The tank line is ONLY used when the aux valve is shifted and a cylinder is retracting or extending. When the valve is in neutral all flow us going out power beyond.
Dan
Hosed is too kind a term. The 90s are pipe swivels.
https://www.discounthydraulichose.com/6901-10-06-10-saeorb-male-x-38-npsm-female-swivel-90.html
https://www.discounthydraulichose.com/6901-08-06-8-saeorb-male-x-38-npsm-female-swivel-90.html
Dan