I'VE GOT A SCARAB WITH A PAIR OF 420'S AND IMCO HYD EXTERNAL POWER STEEING .... I'D LIKE TO MOUNT A SECOND POWER STEERING PUMP IN CASE I LOOSE THE STRBRD ENGINE I'D LIKE TO BE ABLE TO STEER.... IS THIS A DIFFICULT PROPOSITION? THANKS IN ADVANCE ED

TTT
I am curious about this also. I think I am just going to add the extra pump, T it all into the system get it all bled out. I will remove the belt and add shutoff valves or directional check valves.

Check out page 80-85 It about 10 megs and takes a bit to download.
http://www.imcomarine.com/nvcatalog/imco_2009.pdf

CP has a kit that will do this, its around $500 bucks.

Really all you should need is a check valve on each pump, shortly after the pump on the pressure side, then tee the lines together going to the helm. That is assuming you have full hydro... Then a shared overflow reservoir, running the return line from the helm to the shared reservoir, which in turn feeds both pump reservoirs.

My only question is if you would need to add an additional or larger cooler for the additional heat the extra pump will add into the system...

Use a priority valve. Basically a check valve. With both motors running, the valve is in a an equalized input mode. Shut off 1 motor, the valve blocks off the no input port and uses the working input port. No manual switching to be needed.