Garmin GPS 551 NMEA speed out

[RogerJolly]

Hello folks.

Can I get my old Garmin GPSMAP 551 plotter to output NMEA Speed, to be an input to my Raymarine autopilot? I need a backup to the
paddlewheel speed input that rarely works.

Been struggling to find information on how to configure this.

Maybe that's because it's easier than I think though, and you just hook up the plotter to the
Raymarine network, then through the magic of NMEA 2000 the autopilot says "anyone got
speed data?" and the plotter says "here you go"?

Would need an adapter cable to connect up the plotter I think.

Many thanks

 

[lustyd]

NMEA is a broadcast, so no device needs to ask for anything, they all just blurt out what they know and the others listen for what they need. Usually you have to filter based on the sender you want to listen to.

I don't know if it sends gps speed, sorry. It will be on the back pages of the manual though usually.

 

[salar]

According to the manual, https://static.garmin.com/pumac/GPSMAP_400-500_OM_EN_US.pdf page 48 you can select NMEA 0183 VHW which is water speed and heading. That is simple wiring. If you don't already have a NMEA2000 network and want to use that instead, you will need a power input unit, two drop cables, two end caps and three T connectors to join the Garmin and Raymarine units together!

 

[TSB240]

According to the manual, https://static.garmin.com/pumac/GPSMAP_400-500_OM_EN_US.pdf page 48 you can select NMEA 0183 VHW which is water speed and heading. That is simple wiring. If you don't already have a NMEA2000 network and want to use that instead, you will need a power input unit, two drop cables, two end caps and three T connectors to join the Garmin and Raymarine units together!

I thought the op was trying to use sog as a replacement for his unreliable water speed as provided by his paddle wheel?
How does a gps magically supply water speed without reference to a paddle wheel?

I am interested as I have a similar problem with my b and g network pilot ap that requires a working paddle wheel input to remain operative. I was hoping given rare paddle jamming to feed it a gps speed signal until the paddle can be pulled and cleaned.

 

[QBhoy]

Hi. Might not be relevant, but Im all but certain that the very similar almost identical 450 and 550 are NMEA 0183.

 

[salar]

I thought the op was trying to use sog as a replacement for his unreliable water speed as provided by his paddle wheel?
How does a gps magically supply water speed without reference to a paddle wheel?

I am interested as I have a similar problem with my b and g network pilot ap that requires a working paddle wheel input to remain operative. I was hoping given rare paddle jamming to feed it a gps speed signal until the paddle can be pulled and cleaned.

This is the OP's question that I am answering: "Can I get my old Garmin GPSMAP 551 plotter to output NMEA Speed, to be an input to my Raymarine autopilot? I need a backup to the paddlewheel speed input that rarely works. " A GPS magically supplies the VHW sentence through NMEA, which is listed as Water Speed but without a sensor I'm assuming is SOG. It's all there is, anyway.

 

[salar]

Hi. Might not be relevant, but Im all but certain that the very similar almost identical 450 and 550 are NMEA 0183.

From the manual: "NOTE: The GPSMAP 431/431s and GPSMAP 531/531s are not NMEA 2000 compatible. " It doesn't mention 551.

 

[QBhoy]

From the manual: "NOTE: The GPSMAP 431/431s and GPSMAP 531/531s are not NMEA 2000 compatible. " It doesn't mention 551.

Sounds like the wrong manual. But as far as I know, the 451 and 551 replaced the 450 and 550 I have. They are both nmea0183 compatible

 

[PaulRainbow]

Sounds like the wrong manual. But as far as I know, the 451 and 551 replaced the 450 and 550 I have. They are both nmea0183 compatible

They both support NMEA 0183, but the 551 also supports NMEA 2000, the previous models do not.

 

[PaulRainbow]

Hello folks.

Can I get my old Garmin GPSMAP 551 plotter to output NMEA Speed, to be an input to my Raymarine autopilot? I need a backup to the
paddlewheel speed input that rarely works.

Been struggling to find information on how to configure this.

Maybe that's because it's easier than I think though, and you just hook up the plotter to the
Raymarine network, then through the magic of NMEA 2000 the autopilot says "anyone got
speed data?" and the plotter says "here you go"?

Would need an adapter cable to connect up the plotter I think.

Many thanks

Which model of autopilot do you have ? If it's an older model with Seatalk you would need a way of connecting the plotter by NMEA 0183, or, fit something like a Seatalk to STNG convertor and use an adaptor cable. If it's a model that's using STNG all you need is an adaptor cable.

That said, whilst the GPSMAP 551 supports PGN 128257 (Speed Water Referenced) it cannot output it without it being an input too. STW would need to be on the network for the plotter to output it, which is pointless, because if it was on the network you wouldn't need to connect the plotter.

The plotter would have SOG data but the autopilot may not use it. So again, which autopilot do you have and is the firmware fully up to date ?

 

[RogerJolly]

Thank you for the replies – great help.

Yes, shooting for Speed Over Ground sourced by the plotter. Thinking this is better than nothing, even if out by a knot or two tide speed. This post STW vs SOG for Evolution Autopilot Speed Input is the impetus for it all.

AP is an Evolution hydraulic job that came installed on the boat, so there’s a SeaTalkNG network.

The firmware update issue is the crux of it. Simplest solution is to add a Raymarine MFD to system, for downloading and installing latest firmware. Added benefit of native compatibility with AP. Would probably go for an Axiom 7. (Bit of a bummer needing an MFD for firmware updates. Keep searching for some kind of workaround but no luck so far.)

Cheaper option, as per original posting, is probably getting the local boat yard to update the firmware, while buying an adapter cable to put the old 551 plotter on the network. (I understand the Raymarine network uses NMEA 2000, with ‘Seatalk’ referring to the physical cabling, so plotter and AP would see each other). Would I be nearly there then (Paul R)?

 

[PaulRainbow]

Thank you for the replies – great help.

Yes, shooting for Speed Over Ground sourced by the plotter. Thinking this is better than nothing, even if out by a knot or two tide speed. This post STW vs SOG for Evolution Autopilot Speed Input is the impetus for it all.

AP is an Evolution hydraulic job that came installed on the boat, so there’s a SeaTalkNG network.

The firmware update issue is the crux of it. Simplest solution is to add a Raymarine MFD to system, for downloading and installing latest firmware. Added benefit of native compatibility with AP. Would probably go for an Axiom 7. (Bit of a bummer needing an MFD for firmware updates. Keep searching for some kind of workaround but no luck so far.)

Cheaper option, as per original posting, is probably getting the local boat yard to update the firmware, while buying an adapter cable to put the old 551 plotter on the network. (I understand the Raymarine network uses NMEA 2000, with ‘Seatalk’ referring to the physical cabling, so plotter and AP would see each other). Would I be nearly there then (Paul R)?

You're correct about STNG, it's just N2K with different cables/connectors. So a STNG to devicenet cable will allow you to connect the plotter to the network (you will likely need to add a tee connector to the network, unless you have a spare port on a five way connector).

Once connected, you can set the speed source from the AP controller, assuming an appropriate controller and software up to date enough to have the feature (early controllers didn't have the option).

It's also worth noting that the AP doesn't actually need STW. Early versions of the software didn't react well to the loss of STW, although they worked fine if it wasn't connected. Up to date software doesn't have that issue, although you might get a message if speed is lost.

As far as i know, the only way to update the AP is with a STNG MFD, doesn't have to be an Axiom. You can of course get the boatyard to do it.

 

[salar]

Sounds like the wrong manual. But as far as I know, the 451 and 551 replaced the 450 and 550 I have. They are both nmea0183 compatible

It's the correct manual covering both models - accessed from the Garmin 551 product page. 551 is NMEA 0183 compatible and the reference to NMEA2000 in the manual includes the 551. If the OP can use NMEA 0183 I think it will be a whole lot simpler but only if the AP can receive that protocol obviously.

 

[PaulRainbow]

It's the correct manual covering both models - accessed from the Garmin 551 product page. 551 is NMEA 0183 compatible and the reference to NMEA2000 in the manual includes the 551. If the OP can use NMEA 0183 I think it will be a whole lot simpler but only if the AP can receive that protocol obviously.

The AP is STNG, it cannot receive 0183 and even if it could, the plotter cannot output it as it doesn't have a STW input.

 

[QBhoy]

It's the correct manual covering both models - accessed from the Garmin 551 product page. 551 is NMEA 0183 compatible and the reference to NMEA2000 in the manual includes the 551. If the OP can use NMEA 0183 I think it will be a whole lot simpler but only if the AP can receive that protocol obviously.

Got you. Good info above.