My boat and motor were totally custom, I'm using a WIX 3522 filter/separator on a custom mount with -8 Stainless braided lines. After doing some pump homework, I noticed that the Merc and Carter pumps are virtually identical. I figured any difference was the diaphragm and valving.

CV products in Mooresville NC has a billet pump to replace the Carter pump. It has way better valving and is available with differant springs for higher pressure if desired.
http://www.cvproducts.com/ProdDet.aspx?PN=SPIN-MP-2518

The seawater pump mounted fuel pumps that are used on carbed HP500's, 525sc's, and 600sc's are 120gph. I can't swear to it that the same units are used on lower HP 502's and 454's. Looking back at ThisIsLivin's posts, I'm not sure what the original platform was for his build.

Brad at Nickerson Performance originally gave me that info, and I was a bit skeptical myself. After doing my own research with some folks at Mercury, they confirmed what he had told me.

I just pulled a Carter 130GPH and Merc Pump apart and they are identical. The check valves, diaphragm, casting, everything is identical. FWIW

I will add that doing some research on the Merc fuel pump part number showed that it was also used on many Merc V8 motors as well. That pump is more then you think it is. However, Merc does not offer a rebuild kit. I choose to go the CV route. Appreciate guys the info on the Wix seperator.

This is the CV unit that I choose to replace the stock Merc unit with. We are talking about the Merc part #861677T correct? In talking with CV, this is their replacement pump.
http://www.cvproducts.com/ProdDet.aspx?PN=SPIN-MP-2630