Mine are mounted within five feet (or actuall closer) to my unit. They need to be below the waterline for ease of priming. You will have to match the gph with Mfg reccs. They should have that in their write-up or can answer. In my experience, it is not the GPH of the pump that is critical, it is the strainer(s) that clog up and have to be cleaned that shut down the pump. I think I mentioned all that in a differnet thread, though.
As far as its location, Cam could be right. He typically is (well, except about who makes the worlds finest yacht). Double check with the pump mfg for specifics. However, if it were me:
1) My T-Hull would have an outside strainer on it. http://www.westmarine.com/webapp/wcs...allpartial/0/0
It would be mounted low on the boat. It would have a "t" fitting that we discussed earlier.
2) Just outside of the T-Hull I would have a large Bronze strainer. http://www.westmarine.com/webapp/wcs...llpartial/30/0
I would NOT use that piece of junk little strainer they give you.
3) I would make the R-Water run to my a/c RW pump, which would be below the waterline. It is neccessary that this pump and the strainer and T-Hull all be easily accessible. I would put the strainer beside the T-Hull instead of beside the pump for ease of cleanout. The pump must be accessible to make it easier to reprime. The more accessible, the better.
4) Put your compressor wherever you want, but discharge to an easy to see location because this is how you will make sure you really are making/moving water and it is also how you will see if your water flow is getting impeded. I would not discharge underwater.
Hope that helps.