I am not sure about your question,have not heard or seen any -300 with aux fuel tanks.
a bit of your question:
The B737 200/500 could have one 1500kg tank in aft cargo. And the -400 could have two 1500kg tanks in aft cargo.
The aux tank for the -200 was installed by Boeing, and the Aux tank for the 400/500 was retrofitted by Rogerson as a customer option.
The BBJ has options for 7 or 8 aux tanks in both fwd and aft cargo compt.
For your reply,very kind of you.What's strange that I am presently looking at a 737-3/4/500 Fuel system schematic and it shows in the diagram a centre tank,maybe I am confusing myself thinking a centre is the same as a auxilary tank.Can you please comfirm the possibility of a centre tank.
Thanks very much
According to a USAirways ops manual I have, some of their 737-300s and -400s have aux tanks. The capacity is as follows:
Maximum Fuel Quantity (at a density of 6.7 lbs/gallon):
Each wing tank: 10,000 lbs
Center tank: 15,500 lbs
737-300 Aux Tank (if installed): 2,800 lbs
737-400 Aux Tank (if installed): 3,300 lbs