Seatalk & NMEA

There are several hardware devices that will provide translation and conversion of Seatalk/SeatalkNS to NMEA.

See these forum threads:

Seatalk/Seatalk1 (3wire) to Nmea 0183  Bidirectional   "Seatalk LInk"
The devices provided here are quite good.
I am using Tiny SeaTalk NMEA Bridge with galvanic isolated USB. Good support.

Nmea 0183 to  Nmea 2000
Articsense NGW-1  (two programmable versions one for Instruments, another includes AIS)
The Actisense NMEA 2000 to NMEA 0183 Gateway is the easiest way to link between a boat’s old and new data networks.  Bidirectional converter from NMEA 0183 to NMEA 2000. Allows use of NMEA 0183 devices on NMEA 2000 network. 10-35 VDC.

Nmea 0183 to SeatalkNS to Nmea2000

Articsense NGW-1-STNG  Convert NMEA 0183 data into SeaTalk NG and vice-versa, providing seamless integration with Raymarine products. The NGW-1-STNG option combines a standard NGW-1-ISO with a Raymarine SeaTalk NG adapter cable to interface legacy instruments to the NMEA 2000 based SeaTalk NG bus. 
Now available with the SeaTalk NG to NMEA 2000 adaptor Cable - STNG-A06045
Conversion Sentences List:

See these links:
Excellent overview of Seatalk, Seatalk1, SeatalkNS:
Boat Projects: Beginners Guide to Raymarine's Seatalk and Derivatives

Raymarine Seatalk or Seatalk1 to/from Nmea0183 Bridge Converter E85001

Raymarine NMEA Multiplexer E55059

Raymarine SeaTalk NG Networking
Raymarine NMEA 0183 Multiplexer

Raymarine Seatalk - NMEA bridge for Brookhouse multiplexer

Thomas Knauf a SeaTalk Technical Reference

Shipnetwork OpenSeaMap-dev

For direct connection to PC or Laptop device use an FTDI USB to Serial Converter.
USB RS232 Cables
From Jamestown Distributors Website

The E55053 SeaTalk 2 / NMEA 2000 Interface Cable (1.5m) is for connecting E-Series displays to Raymarine SeaTalk 2 or 3rd party NMEA 2000 Devices. The SeaTalk 2 / NMEA 2000 Interface Cable features a twist-lock connector at the E-series display end, and a standard 5-pin waterproof SeaTalk 2 style connector at the other.

The E55054 SeaTalk / Alarm Output Interface Cable (1.5m) is for connecting E-Series displays to Raymarine SeaTalk instrument networks. Also supports connection to an external alarm. The SeaTalk / Alarm Output Interface Cable 6-Pin twist lock connector a E-Series display end, and wire leads at the other.

The E85001 PC/NMEA/SeaTalk Interface Box converts signals between SeaTalk, NMEA 0183, and RS232 formats. Enables RayTech navigation software to converse in SeaTalk with compatible devices. Can be used to host PCs running NMEA based navigation software on a SeaTalk network. Also supports operation of the Raymarine Main Alarm when an alarm condition exists on the SeaTalk bus. This item is no longer available

The E86001 PC Serial Data Cable (2M) is used for connecting computers running RayTech navigation software to the E85001 interface box. Also used to tie NMEA GPS units to a PC's serial data port. The cable is fitted with a screw-lock DB-9 female connector on one end, and bare wire leads at the other, suitable for connection to your GPS or PC interface

Seatalk (Seatalk1) to Nmea2000

Raymarine Converter Panbo
Raymarine SeaTalk 1 to SeaTalk ng Converter Kit  
Model #:  E22158  Defender Item #: 254238   $87.99
Works with Select SeaTalk 1 Instruments, GPS sensors and LifeTag, 
Easy Plug-and-Play Connectivity with SeaTalk ng Networks. Good for ST60 Instruments.
Use the Panbo "N2K Cable Mixxing not a big whoop" directly below to connect to Nmea2000.

Modify Raymarine Seatalk NG cable by adding a Nmea2000 Adapter
Panbo:  N2K, cable mixing not a big woop by Ben Ellison and posted on Feb 5, 2008

Raymarine SeaTalk NG To NMEA2000 DeviceNet Male Connector,  Adapter Cable 
Mfg #:
A06046  Defender Item # : 257913   $28.99
NMEA 2000 micro male connector on one end and SeaTalk NG connector on the other end
sed when connecting NMEA2000 standard devices to Raymarine SeaTalkng data network & visa versa.
The adapter cable has a standard white Raymarine spur connection on one end, and a NMEA2000 DeviceNet Male connector on the other. The adapter is approximately 10-inches long.
This adaptor has a DeviceNet connector with pins ("male"). That's what you need to plug into a DeviceNet T-connector as the drop cable.

"I have been advised that these connections will send and recieve data both ways."

"As it turns out, I could not get either of those cables to resolve the ambiquity, and I made my own by cutting some other cables in half and splicing them.
(A male devicenet connector at the tee end of every drop (or "spur" in STng talk) because a standard tee has two female and one male connectors. )   --Seatalk-to-STng converter also produces valid NMEA 2000 PGNs..."

"As far as I can determine, True Wind info is not present on the Seatalk bus, in either Seatalk1 or SeatalkNG, at least in a hybrid system. I have ST60 displays and ST70 pods and displays, and I can only find Apparent Wind data present on either bus. Which means that each display must be calculating its own True Wind data."