Reworking ST40, Seatalk1 system

[TyTy]

We've got a 1982 O'Day 25 that we are refitting, repairing, replacing parts on. We've got the mast down right now, so I figured it's a better time than ever to get a wind transducer, since whatever was there prior was never when we got the boat. Likewise, I examined our displays and wiring and found that, despite previous assumptions, they actually work and just needed some coaxing. We have two Raymarine ST40 displays, so I ordered a new Rotavecta Wind Transducer that I will be installing this weekend. After pulling out our speedo, lubricating it, and seeing it work, I decided it's best to keep our current indicators and displays. I also discovered that we have a digital compass that is not hooked up to anything.

We plan on doing cruising in Long Island Sound and Lower New York Bay, as we did last year.

Here is my schematic of our current system:



Displays:

• Raymarin1e ST40 Wind
• Raymarine ST40 Speed
• Signet Scientific Depth Finder MK172.4

Sensors:

• Speed and Water Temp Transducer
• New Raymarine Rotavecta Wind Transducer (just ordered, to be installed this weekend)
• 200kHz Depth Transducer
• Si-Tex Marine Electric Digital Compass Sensor DC-4008 (not hooked up to anything)

My questions are are:

• To get the speed data to the wind display to we can show the true wind speed, I need a Seatalk1 junction box, with cables running to both ST40 displays and one to the electrical panel. Is this correct? This Raymarine ST40 Interconnect Kit from Defender is all I need, is this correct? I've seen this diagram in the manual PDF I tracked down, does this mean I need two junctions instead of one?
• We have an electronic compass we are not using, is there something we should connect it to?
• Above is the list of our equipment, we currently use Navionics and other apps on phones and tablets to navigate. What display do you think would be a logical next purchase?
• Would it make any sense for us to buy a GPS Receiver Antenna?
• Is there any way to use the current sensors we have to send the data over Bluetooth to Bluetooth devices without having to replace our current displays? If yes, how?

Thanks!

[Opie91]

You do not need a fancy Seatalk junction box. A terminal strip is fine. Just connect like colors/shield together. Yellow-Yellow, Red-Red, Shield(black) to Shield(black). Butt splices would work too, but I prefer the terminal strip since you can add/remove items easily.

The yellow wire is the bus, Red positive and Shield(black) is negative. Use a 5 amp fuse to power the strip.

[TyTy]

Thank you Opie. I will do a butt splice and then take the power to the panel. When I eventually want to push this information to other devices over Bluetooth, is there an existing out-of-box solution?

[Opie91]

I was trying to go in the direction you are. In the end it was cheaper to sell what I had and buy NMEA 2000 stuff. It is easier and a lot better.

Wifi options are cheaper for putting info out. Try Home - Madman Marine Electronics

Seatalk to bluetooth is going to cost some $$$$. I think Brookhouse makes one, but it is expensive and their support is poor (my experience).

Just my opinion here: Get what you have working and save up for a NMEA 2000 system. In the end you will probably get there anyway.

[Ex-Calif]

Originally Posted by Opie91

I was trying to go in the direction you are. In the end it was cheaper to sell what I had and buy NMEA 2000 stuff. It is easier and a lot better.

Wifi options are cheaper for putting info out. Try Home - Madman Marine Electronics

Seatalk to bluetooth is going to cost some $$$$. I think Brookhouse makes one, but it is expensive and their support is poor (my experience).

Just my opinion here: Get what you have working and save up for a NMEA 2000 system. In the end you will probably get there anyway.

Yeah, ya gotta live with the limitations of the ST40 line.

I have ST40 depth and speed - I've dreamed of wind but the bucks aren't worth it to me.

As a "mental" exercise I did wire up the seatalk and even made a cable to interface with my "old" Garmin 276 including my Tiller Pilot ST2000.

It all ended up working for a while the Garmin was sending steering instrucitons to the TP and receiving speed data and so on.

Wiring the seatalk up is easy just use terminal strips and connect all the yellow wires together.

You may end up with strange results - I learned way to much about NMEA183(?) words and bits. NMEA2000 is pretty different. It wsa geeky but like I said a mental exercise.

The Garmin is gone the depth and speed are still wired to each other and Otto is once again commanded by me...

For a new build I'd get new stuff. For an older boat used ST40 stuff can be had. I originally had only depth - the screen fried and I picked up the depth & speed together on Craig's list or something for like $100.

It was worth it to me.

[TyTy]

Just my opinion here: Get what you have working and save up for a NMEA 2000 system. In the end you will probably get there anyway.

Maybe on the next boat! I don't know if this 1982 O'Day 25 is worthy for more investment of that sort.

As a "mental" exercise I did wire up the seatalk and even made a cable to interface with my "old" Garmin 276 including my Tiller Pilot ST2000.

It all ended up working for a while the Garmin was sending steering instrucitons to the TP and receiving speed data and so on.

In all likelihood, this is the extent that would be very useful for us and maybe we could go this summer. I'd like to extract the data and send it to a phone and other devices and work on some app ideas, but if NMEA 0183/Seatalk1 is too phased out then that might not make sense at this juncture.

[Jubilee39]

The shipmodule nmea multiplexor does a good job of taking in seatalk and broadcasting over bluetooth along with other capabilties

[SailFastTri]

Originally Posted by TyTy

Thank you Opie. I will do a butt splice and then take the power to the panel. When I eventually want to push this information to other devices over Bluetooth, is there an existing out-of-box solution?

I think you'll need to convert Seatalk to NMEA 0183 (Raymarine makes or made a converter) then convert 0183 to Bluetooth. A lot of effort and expense for little reward, unless you're a geek who does these things for pleasure. I think you're wise to stay with the ST40 for now but I think you'll find Rotavecta isn't very accurate for small wind variations in light air (under 5kt apparent).

BTW I find the only time I really like to use true wind display is when running downwind, and that's for safety reasons in case we stuff or round up. At all other times I'm trimming for apparent.

[TyTy]

Thanks Jubilee, that is exactly that I am looking for.

I think you'll need to convert Seatalk to NMEA 0183 (Raymarine makes or made a converter) then convert 0183 to Bluetooth. A lot of effort and expense for little reward, unless you're a geek who does these things for pleasure.

SailFastTri, thanks for the reply, I'm a geek who does these things for pleasure!

I think you'll find Rotavecta isn't very accurate for small wind variations in light air (under 5kt apparent).

I figured that by its price and its oddball design (the tab'd hemispherical cup on the anemometer). I was $230 including the cable and was designed to work with the display that we already had. I'll get something better on our next boat.