I am looking for 2 new pumps to replace my old ones. One doesn't work any longer and one leaks due to a crack in the outlet tube.

All I can find are one that mount to the hull or transom. I don't want that. I am specifically looking for 500gph, 12 volts, single output, that just sits in the bilge area.

Does anyone have any suggestions?

If you get the regular transom mount pump get the 90 degree pump. It should look like this. https://www.google.com/search?q=johnson+90+degree+aerator+pump&biw=1164&bih=265&source=lnms&tbm=isch&sa=X&ei=hE21VIHgHYb8yQTSs4KABA&ved=0CAcQ_AUoAg#imgdii=_&imgrc=o4nW3eIQ2E5OCM%253A%3BSAnFLqx50oPy3M%3Bhttp%253A%252F%252Fassets.suredone.com%252F1814%252Fmedia-photos%252Fsd0157-johnson-pump-cartidge-livewell-aerator-pump-90-degree-750-gph.jpg%3Bhttp%253A%252F%252Fshockeysboats.com%252Fjohnson-pump-cartidge-livewell-aerator-pump-90-degree-750-gph-sd0157%3B1024%3B768They come with an adapter (shown in the bottom right of the pic) if you don't want to mount it directly to the transom.