Yes, according to the Mozambique consulate in Washington, DC with whom I spoke, you need a transit visa. Also for citizens of countries with a Mozambique embassy you must obtain a visa prior to arriving in Mozambique as they will not give you a visa on arrival. More info can be found on their web site when it is working, and often it isn't:
http://www.embamoc-usa.org/index.php...d=89&Itemid=64
Visa for US citizens is $160. You may also call the Embassy's consular services and inquire Mon-Thur from 3:00 to 5:00pm EST. (202)-293-7147 ext 230 Ask them to email you Visa requirements information. I would copy and paste the info from that document, but it is actually an image, so there is no text to copy and paste.