9 pin to usb adapter

[AngusMcDoon]

I made a similar thingummy but rather than transferring AIS via RS232 to USB it converts Seatalk to USB in NMEA data format. It's very similar to the cheap item that the OP described, but also does some protocol conversion from the Seatalk data format to NMEA data format.

It's all described here...

http://www.ybw.com/forums/showthread.php?t=278332