Advice for New Transducer and (Perhaps) Chartplotter

[_Ish_]

Hi all, I need to get myself an operational transducer for my E25+. The original does not appear to work and the transom mounted one that came with the boat when I purchased it does not talk to the Garmin GPSmap 498 that’s… 20yrs old? I am a novice sailor who is eager to get out, explore, and do weeklong cruises. But I currently can’t even anchor up anywhere given that I live in Alaska’s fjords and the depths are typically several hundred feet until you get right up near shore.

Does anyone have recommendations for getting a working transducer without hauling the boat out? I’ve heard that some older boats you can actually unscrew the transducer, cork it with a provided plug, and clean them. A friend did this and was able to swap the old transducer with a new one that fit the threads correctly. Is this an option with the E25+? Is there a way to have a transducer talk to a tablet with Navionics or something similar in lieu of a chartplotter? Since I’m in Alaska, there is very little cell service which means I could not be reliant on anything that requires a consistent internet connection.

With the Garmin is so old, I assume I need a new chartplotter and will perhaps get other sensors if it makes financial sense. However, all the boats I work on have integrated bridge and/or ECDIS systems so I don’t really know what options are for piecing together an affordable system for my little sailboat. When I talked to the guy at West Marine it sounded like my options started at $700 for anything better than a lakeboat fishfinder. Is this really the case? Would I fare better on ebay?

Any guidance or advice will be much appreciated.

 

[peaman]

Does anyone have recommendations for getting a working transducer without hauling the boat out? I’ve heard that some older boats you can actually unscrew the transducer, cork it with a provided plug, and clean them. A friend did this and was able to swap the old transducer with a new one that fit the threads correctly.

Speed transducers which can be removed without hauling are common. Same for combination speed and depth. Newer ones have a built-in valve to greatly reduce the water flow when the transducer is removed, which results in less anxiety while you try to get the dummy plug into the through hull opening. Because most through hull transducers are made by Airmar and sold under various names, it may be possible to install a new transducer in an older through-hull fitting. Just be prepared for the flooding when the transducer or plug is removed, as it can be pretty frightening for the uninitiated.

As for depth transducers, they are available for in-hull installation. Carefully review the installation requirements and pro/con arguments before purchase. There are a few in-hull depth transducers on eBay, for those who don't mind gambling a bit.

With any purchases of new or used electronics, make sure you understand what cabling is needed. Your old Garmin is probably NMEA0186 or even proprietary. Modern stuff is usually NMEA 2000 which simplifies wiring and compatibility between devices.

 

[Slick470]

Hard to say if a new transducer will install in the same hole as the old one without doing some research on what you have vs what you are planning on buying. As peaman mentioned Airmar has manufactured a large percentage of the transducers for the recreational marine market and they sell them to most of the major instrument manufacturers. I have heard of people being able to swap out the transducer without replacing the thru-hull housing but I personally didn't chance it when I upgraded, but it does require a haul out to swap the housing.

The newer thru hull devices are often tri-ducers that combine speed/depth/temp in a single device, so while the overall system may cost more than you are expecting, it can give you a lot more information or flexibility if you want to expand things later.

The little flapper valve that peaman mentioned that is supposed to slow the water ingress while changing out the transducer with a blanking plug on newer style through hulls is a nice thought but they are notoriously fragile and can break off. Mine disappeared not long into it's life. It was nice while it lasted.

 

[peaman]

The newer thru hull devices are often tri-ducers that combine speed/depth/temp in a single device,

I don't know if this issue has been fixed, but a number of those "tri-data" devices, or "DST" (Depth-Speed-Temperature) devices had faulty temperature sensors. I have one from B&G, purchased in 2021, which works fine for speed and depth, but the temperature only worked for a year or so. But then I won't really miss it until I want to cross the Gulfstream.

To install that DST device, I needed to replace the through-hull fitting, which for me was not as difficult as I feared. I wrote about how I did it here.

 

[Christian Williams]

You need a new chartplotter, and a depth transducer. $700 range sounds right. Airmar makes in-hull transducers, meaning no hole, shoots through the hull, so no need to haul. They work for me up to 400 feet or so.

It is deep here, too, and because of that I find little real need for a fathometer. GPS says where I am, which is good enough. A modern chartplotter is much more important than depth in my environment.

 

[Slick470]

I don't know if this issue has been fixed, but a number of those "tri-data" devices, or "DST" (Depth-Speed-Temperature) devices had faulty temperature sensors. I have one from B&G, purchased in 2021, which works fine for speed and depth, but the temperature only worked for a year or so. But then I won't really miss it until I want to cross the Gulfstream.

To install that DST device, I needed to replace the through-hull fitting, which for me was not as difficult as I feared. I wrote about how I did it here.

Ours initially wouldn't display the temp, but found a buried check box in a menu somewhere. I haven't heard about the sensor being faulty on them, but good to know as something to look out for. Ours has been in service since 2014 or so.

I think ours probably would have fit in the old speed log hole and the threads appeared to match up, but I wasn't willing to risk it. I was able to re-use the hole in the boat with out making it larger or needing to fill in, but was left with an extra hole from the old depth transducer that I ended up glassing back in. Overall a relatively easy boat project with a bit of planning.

 

[_Ish_]

Apologies for the delayed reply. Our ship's internet has been down.

I appreciate all the info and opinions. Doing an In-Hull seems like it'll be the easiest way to go and if they are generally around the price of that $90 Airmar P79 that was linked to, that is an easy investment to make. Now I'll just need something to display the information. Is a chartplotter necessary for these or can these be linked to tablets, phone via app, etc.?

I work on water taxis in my area and am more familiar with the various random hazards than the Garmin maps seem to be as there are lots of submerged rocks and sudden shallows up here. But I use the free iNavX app as a redundant system when I'm working and it seems to be as informed as the expensive Garmin systems the boats have. Having said that, the plan is to start going farther out and getting a few days sail away from familiar waters. So, again, a new chartplotter is definitely in the future. But if I can get a functioning depth transducer without it then I may be able to take my time to shop around and figure out exactly what I'd like for this boat (and probably the next) before I drop $700-$1000. Peaman mentioned most modern stuff being NMEA 2000. Does this mean that all of these things (chartplotters, speed logs, depth transducers, etc.) are fairly interchangeable and universal now?

Regarding the possibility of swapping out the original transducer with a new thru-hull one, I have all my cold water dive gear and plan to get in and clean the hull anyways. So putting some sort of plastic etc. over the hole would be an easy way of mitigating water coming in during the swap. Perhaps reaching out to the company would give me the info to find one that will be compatible with the diameter and threads. On the other hand, if there's no real advantage to a new thru-hull vs the in-hull then I might as well let well enough alone and not a leaky boat.

Thanks again for the help.

 

[Slick470]

Peaman mentioned most modern stuff being NMEA 2000. Does this mean that all of these things (chartplotters, speed logs, depth transducers, etc.) are fairly interchangeable and universal now?

yes, to a point. Basic stuff like wind/speed/depth instruments will pretty much work on anyone's system so you can mix and match the various manufacturer's transducers, displays, and chart plotters, even NMEA 2000 enabled VHF and AIS. This is because the manufacturers us a standardized sentence/device format within the NMEA 2000 protocol for that data. Where things get a bit wonky is for autopilots (and probably other more specialized gear) as there is no standard for that data so each manufacturer does their own thing. So... if you really want an AP at some point that is connected to the rest of the system, then sticking with the same brand family makes sense. You can still get it to work, but the integration isn't seamless.

For example, our boat has a B&G Triton W/S/D system with two displays. I added a Lowrance VHF with AIS that is NMEA 2000 and a B&G Vulcan chart plotter. These all work seamlessly on the network because Lowrance is a Navico brand along with B&G and Simrad. My boat is a tiller boat, so to add a AP a tiller pilot made the most sense. At the time Raymarine made what seemed to be the best option so I have a Ray Evo tiller pilot system on the boat too. Ray had a proprietary cabling network at the time (maybe still do), So I have two networks on my boat, a standard NMEA 2000 network and a Raymarine one. They are tied together with an adapter cable so the AP can see speed, wind, and nav data off the B&G system and the B&G system can use the Raymarine heading sensor for it's calculations. Sounds pretty good, except for where the AP comes in. If I had a Raymarine chart plotter, I could fully control the AP through the chart plotter. The B&G chartplotter tells me there is no AP on the network even though it can see other devices on the Ray side. There is a workaround where you input a course on the chartplotter, then tell the AP to "go-to" or "follow" or something along those lines (it's been a bit) and it will follow the course. It's clunky but it works.

The other advantage to sticking with the same brand family is applying updates. The manufacturers are extending the useful life by adding functionality (and fixing bugs) to these devices by putting out updates. For most manufacturers you apply these updates through the chartplotter (or MFD) and that has to be the same brand family as the rest of the devices on the network. So, I can update everything on my network via the B&G Vulcan except for the AP. I need a Ray AP to apply updates to that. Now of all the devices, the chartplotter is the one that will benefit the most from updates, you may find yourself with the need to update the AP like I did to fix a pretty major bug.

 

[peaman]

That's a really good summary.

 

[gabriel]

This is a budget chart plotter which also has AIS class b transponder:

Onwa AIS chart plotter

 

[_Ish_]

Thanks Slick470 for putting that together. It was really helpful. Now that I've got a better understanding I can start digging into it all and figuring out what will work for me.

I'll read up on that Onwa. Thanks Gabriel.