On Sat, 19 Aug 2006 02:55:56 GMT, Don W
wrote:

Our Irwin 38 only has a 70 gallon
tank. You think that's bad? The holding tank is
only 8 gallons.

After 8 gallons you are supposed to "go" off shore. :-)

You are clearly a candidate for a Y-valve and/or macerator pump.