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Raymarine Wheel Drive plus B&G Autopilot?

Aug 21, 2021
3
Hunter 35.5 New Orleans
Hi everyone. I recently bought a 1995 Hunter Legend 35.5 with a Raymarine autopilot system which uses the ST4000 wheel-mounted rudder drive unit. The other electronics on the boat are now-deceased Autohelm stuff. I’d like to replace everything with B&G equipment, but the boat is too small to accommodate any other rudder drive unit and so I have to stick with the ST4000.

Does anyone know whether the B&G/Simrad NAC-3 autopilot computer will work with the Raymarine ST4000 wheel-mounted rudder drive unit? To me the motor on the ST4000 appears to be a plain vanilla reversible 12v DC motor, and the NAC-3 controller appears to be able to drive any reversible 12v DC motor.

Any guidance on this would be a great help. Thanks!

Mike C.
 
Aug 7, 2021
1
Hunter 340 Port Superior Marina
I have a 1999 Hunter 340 and want to do the same. Any progress? Any advice on the list of B&G products that I should get? I need a Wind Direction Speed indicator, Chartplotter, and Autopilot at a minimum. I assume that there must be a whole ship replacement kit? Did you come across anything like this? Any advice or experience is welcome.

Thanks,

Eric Steege
S/V Endeavor, 1999 Hunter 340
Bayfield, WI
 
Aug 21, 2021
3
Hunter 35.5 New Orleans
Hi Eric. Re progress on the autopilot question, yes, it appears that the Raymarine ST4000 Mk2 wheel-mounted rudder drive unit will indeed work with the Simrad/B&G NAC-2 and NAC-3 autopilot computers. And no, there’s no whole-ship instrument replacement kit that I know of, but I’ll give you my thoughts on that below.

Concerning the autopilot, the ST4000 was originally installed as the rudder drive module of an older Raymarine SmartPilot X5 Wheel system. The ST4000 bolts to the spokes on the ship’s wheel and is pretty much nothing more than big drive belt and a reversible 12vdc motor with a sprocket on its shaft. The first piece of evidence that the ST4000 can be used in an upgrade came from Raymarine’s website documentation, which specifically says that the ST4000 will work with Raymarine’s new Evolution Autopilot system. Second, a B&G tech support rep told me on the phone that the NAC-2 and NAC-3 can drive any reversible DC motor within their power capacities. And for confirmation and comfort, I found on the Jefa Steering website a sprocket drive motor with an autopilot computer compatibility table that lists both the Raymarine Evolution and the NAC-2/NAC-3. So I’m now planning to go ahead and buy the NAC-2, since it’s less expensive than the NAC-3 and can handle the relatively low 5-amp power draw of the ST4000.

What’s actually going on with these modular Raymarine and Simrad/B&G autopilot systems is that their computer units all use DC current at a fixed voltage to operate the rudder drive motor, controlling the direction of the motor via the polarity of the current and varying the torque and speed of the motor by using pulse width modulation of the constant 12-volt (or 24-volt) output to change the effective voltage seen by the motor. The computers all have only two pairs of terminals for their rudder drive outputs, one pair for the clutch and one pair to operate the motor. After the computers are calibrated they’ll appropriately drive any reversible DC motor connected to the motor terminals. (The ST4000 has a manual clutch, so I won’t need to use the clutch terminals on the NAC-2.)

However, one important thing to note is the need to include a rudder position indicator in any of these autopilot systems. The NAC-2 will take rudder inputs either from a resistance-based rudder feedback unit or a NMEA 2000 data-based unit. The Simrad/B&G data-based RF25 unit is short enough to fit in my boat, so I’ll use the RF25 with the NAC-2.

This brings me to the second part of your question. I haven’t purchased the autopilot system yet because I’m currently focused on installing the various pieces of B&G equipment that I already bought. These consist of two Triton2 displays, a DST sensor, a GPS/compass, a wind instrument, and some NMEA 2000 cable and connectors, all of which were included in the “B&G wired wind package with two Triton2 displays” that came from Defender Marine. In addition to the NAC-2 autopilot components I want to add a chartplotter (probably a Vulcan 9) and a WR10 bluetooth remote control for the autopilot. Also, B&G strongly recommends adding a physical standby key to the autopilot system, and that physical key can be either the Triton2 Autopilot Controller (which is a $300 keypad) or a simple momentary pushbutton switch. Since I’ll have the WR10 remote I’ll probably skip the keypad and go with the pushbutton to save $300 and be able to make a smaller mounting hole in the boat. I might also add a ForwardScan through-hull sonar transducer at some point since the Vulcan chartplotters have a direct plug-in for those transducers.

If anyone has additional thoughts on any of this I’d love to hear them!

Mike
 
  • Like
Likes: Scott T-Bird
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
My only thought is ..... fantastic research! I have planned to do the exact same thing with regard to the Triton Displays and the Vulcan CP. I hadn't really thought out what to do with my ST4000 Autopilot. Now I have a great source of info! :biggrin:

@esteege , I had the B&G Triton package that Mike lists above on my Starwind. I only had it for a year before selling the boat. I was greatly impressed & plan to do the same thing on our Catalina for replacing the current instruments. I also had the Vulcan 7 CP and thought it was great, only I will go with 9 inch minimum or even larger when I upgrade. I won't add the sonar as all we can look at is miles and miles of a flat plain of sand in our location.
 
Last edited:
  • Like
Likes: Ward H
Mar 20, 2004
1,659
Hunter 356 and 216 Portland, ME
Thanks Mikesea! I plan to do the same thing with my st4000. I'm running the same B&G system as you except that I have two zeus displays and the forwardscan transducer - really useful here in Maine - pretty much anything we might hit is rock;)
 
Oct 26, 2008
4,991
Catalina 320 Barnegat, NJ
However, one important thing to note is the need to include a rudder position indicator in any of these autopilot systems. The NAC-2 will take rudder inputs either from a resistance-based rudder feedback unit or a NMEA 2000 data-based unit. The Simrad/B&G data-based RF25 unit is short enough to fit in my boat, so I’ll use the RF25 with the NAC-2.

..... Since I’ll have the WR10 remote I’ll probably skip the keypad and go with the pushbutton to save $300 and be able to make a smaller mounting hole in the boat. I might also add a ForwardScan through-hull sonar transducer at some point since the Vulcan chartplotters have a direct plug-in for those transducers.

If anyone has additional thoughts on any of this I’d love to hear them!

Mike
I was looking up these components and thought there might be incompatibility between WR10 & NAC-2. Both West Marine & Defender list compatibility with NAC-1 but not 2 or 3 (perhaps I was reading something incorrectly). In any case it didn't make sense and looking at the Simrad website, it confirms compatibility with all three core packs.

I think I would do exactly as you describe except I might not do the remote and opt for the keypad mounted at the helm instead.