Any idea what would cause my power steering to only work under power? Idling it quit working and is hard to turn wheel but under power it works like a dream. Any suggestions?

loose belt, blocked hydraulic filter(if hydraulic helm), worn out pump

Pump is a new refurb... just installed. Friday it worked great then after a run across the lake saturday I came off plane and it wouldnt work. Are you talking about the filter down in the bilge or is there another filter up at the helm?

If the belt is tight I think the pump is junk, full hyd ? if so ck filter like said above, in pressure line going to helm, where did you pump ? some std automotive ones may not hold up according to hardin marine...

It is an auto pump... was told it was a direct replacement amd has been used by others with the 525. Whats different about the marine pump?

the price!

I had problems with my hyd helm for years, turned out the inline filter at the helm was not rated for the flow rate involved. Consulted a hydraulics guy and he felt that after initial start up I could get away without the in-line, the magnet inside the pump would do the job.
I took it out and now have finger light steering at any rpm.

I used to think the same thing...talked at length to the owner of AGR who does the "marine" pumps, told me they change to a bearing on the shaft vs a bushing, no I used to do steering work years ago and have rebuilt many saginaw pumps and the do have the bushing supports the shaft, now I have never taken one of these $500 marine pumps apart to see if in fact they do change to a bearing setup or not...I did bit the bullet and buy one when I did my full hyd steering a couple of years ago and if did work better with that than the original..so for whats thats work...Rob