Repair Report - Garmin Sonar Transducer

[dfogal]

Hi All:

Ranger Tug 29-S 2015 here.

This spring I took the boat out for its first little spring shakedown cruise. The sonar was doing ‘sawtooth’ images and was unable to resolve the depth under the boat. On my boat the transducer is bonded to the hull behind the generator shelf at the back of the boat but in front of the thruster.

Many of the original components on the boat are getting harder to source and the Garmin In-Hull P79 (or Airmar P79) is now a special order item at most boating stores. The transducer is a NMEA 2000 device. It’s like a metal hockey puck. There is a black plastic cup that is mounted to the hull. The cup is filled with coolant and the metal sensor is immersed in the liquid and the cup and sensor are screwed together. The transducer makes sound, the coolant carries the sound to the hull, the sound penetrates the hull into the water below the boat.

The diagnostic tree identified by research was - update the software on the chart plotter, open the cup by removing the screws and check that the fluid is still there (if not you fill it and seal it), check that the sensor is operating, check that all the grounds to your chart plotter are working.

In my case we opened the sensor cup and the fluid level was low. We topped it up and sealed it and the transducer is working. Note that if you operate the sensor with low fluid for too long, then the sensor can burn out from the heat. It can apparently put out 600W so maybe 1/3 the heat of a hair dryer. It’s a lot. I use an infrared camera on the boat and it’s very easy to see this.

I thought I would share my repair stories as a start-to-finish in case it helps others.

 

[fishheadbarandgrill]

The transducer is caulked directly to the hull on the R29 Classic.

 

[GarryH]

Thank you for your post. My transducer has been filled 4 times. The last time with mineral oil. In fact, the new 2021 R29cb was delivered to me with no fluid in the transducer cup. Apparently a QC problem at Fluid Motion. Also, Garmin was supportive and sent me a new O ring at n/c. A permanent fix still has not been determined. Dealer refilled cup 3 times and this last time I refilled the cup. I am wondering what you meant by “sealing” the lid before installing the 6 screws. Thank you.

 

[Full_O_Fish]

Just keep in mind that if the base of a P79 has been installed with 5200 rather than a flexible two part epoxy, then mineral oil should be avoided at all costs as it will slowly soften the sealant and eventually cause the bond of the 5200 to fail. Depending on the age, the screws should not need to be removed in order to service (fill) the reservoir. Simply twist the lid roughly a quarter turn and pull up. Common reason for fluid loss is having the o-ring either missing or in the wrong place (for instance between the cap pieces when the screws are removed rather than on the outside of the transducer element between the reservoir and the bottom of the cap).

Comment earlier mentions 6 screws, which would indicate the Garmin GT15M-IH transducer rather than the P79, which indeed would need screws removed to access/service the reservoir. Mineral oil avoidance with 5200 still applies however, best to use propylene glycol.

 

[dfogal]

Thank you for your post. My transducer has been filled 4 times. The last time with mineral oil. In fact, the new 2021 R29cb was delivered to me with no fluid in the transducer cup. Apparently a QC problem at Fluid Motion. Also, Garmin was supportive and sent me a new O ring at n/c. A permanent fix still has not been determined. Dealer refilled cup 3 times and this last time I refilled the cup. I am wondering what you meant by “sealing” the lid before installing the 6 screws. Thank you.

We put a new O-Ring in. I don’t think our fluid leaked between the bottom of the cup and the hull. That means evaporation across the seal.

I find it interesting you filled it so many times! I will have to put this on my list of regular maintenance items.

 

[dfogal]

Just keep in mind that if the base of a P79 has been installed with 5200 rather than a flexible two part epoxy, then mineral oil should be avoided at all costs as it will slowly soften the sealant and eventually cause the bond of the 5200 to fail. Depending on the age, the screws should not need to be removed in order to service (fill) the reservoir. Simply twist the lid roughly a quarter turn and pull up. Common reason for fluid loss is having the o-ring either missing or in the wrong place (for instance between the cap pieces when the screws are removed rather than on the outside of the transducer element between the reservoir and the bottom of the cap).

Comment earlier mentions 6 screws, which would indicate the Garmin GT15M-IH transducer rather than the P79, which indeed would need screws removed to access/service the reservoir. Mineral oil avoidance with 5200 still applies however, best to use propylene glycol.

Thanks. We used antifreeze in the cup. The other detail that surprised me was that the sensor emitted 600W. I also have the old Garmin analog radar! That thing is 4kw of output - the digital one seems to be 50W (not kW). I was surprised by how much power these sensors use.

 

[YukonRon]

I have had issues with my P79 as well. With much fiddling I discovered that the tabs and/or slots that lock the lid in place have worn, and one side kept popping out. I eventually solved it by wegding a small piece of plastic bag in between to fill the slack space. All this while standing on my head in the bilge as my wife piloted the boat through the rapids on our way to the Broughtons! :shock: Now I've been having issues with the sonar losing depth . I've discovered that cranking the gain up to 100% solves it. Having the bottom cleaned soon so hoping that solves it. Or I may be looking for a new transducer.

 

[Full_O_Fish]

Transducer power ratings are just the maximum amount they can be driven with from the respective sounder module. The actual power consumed by a 600W transducer running at full power is around 30W or 3A every hour, this is because the transducer only pulses for fractions of a second similar to an LED dimmer.

 

[GarryH]

Indeed, it is the Garmin 15M. Epoxy was used by the dealer to secure the sleeve to the interior hull. RV (pink) coolant was used the first 3 times. I used mineral oil because I thought the higher viscosity might mitigate leaking. IMO the O ring has a slot in the perimeter of the lid. I ensured that the O ring sat in the slot as I attached the lid to the sleeve. For the past 2 months the plotter has shown a reading that appears to be correct. When the transducer is not operating, the reading is zero. In summary, I do not believe the transducer is leaking at the connection to the hull. The coolant is pink and no residue exists. That being said, evaporation is unlikely given the type of liquid, RV coolant and less than a month. In closing, I don’t know the cause of the disappearing fluid.

 

[gregc]

The transducer is caulked directly to the hull on the R29 Classic.

On my R27-OB, the caulking outright failed -- I had to scrape it and reapply and reseat to the hull.

Mildly had a fit of panic finding pink fluid in the bilge on a gas powered engine................

 

[michaeljgage64]

On my 2019 Ranger OB-27 the Garmin (GT15M-IH) transducer cup has come detached from the hull twice now. First time (1 year ago) it appeared as though the factor bond between the cup and the hull failed. So scrapped everything off, light sanded and re-attached using 3M marine silicone. Re-filled cup with pink non-toxic anti-freeze (propylene glycol). Applied silicone grease to the o-ring seal and re-screwed transducer into cup. One year later (now), started to get erractic depth readings on plotter. Looked at transducer and found anti-freeze leaked out again. Now am in the process of re-attaching the cup.
Ranger Tech. Service said they use Sikaflex 291 at the factory to attach the cup. So guess I will try the Sikaflex 291 this time.
Any suggestions or advice?

 

[Full_O_Fish]

West system G-Flex two part epoxy... Highest bond strength you will get and will completely seal the reservoir to the hull and won't be compromised by any standard chemicals.

 

[GarryH]

Ranger Tech. Service said they use Sikaflex 291 at the factory to attach the cup. So guess I will try the Sikaflex 291 this time.

Authorized Ranger dealer service in Florida told me that the problem with the cup coming detached from the hull in Ranger boats is because the factory uses inappropriate adhesive for the Florida heat. The suggestion for the West Marine resin seems like it would be a solution. Not sure how to remove the cup if needed to be replaced e.g. an upgrade. But that is probably over thinking the issue.
Good luck.

 

[gwishon]

I suspect that, in addition to the Florida heat, vibration plays a large part in causing the cup to detach. The floor below the transom, next to the rear thruster, a spinning prop shaft, the rudder running gear, trim tabs, generator, and engine vibrations— there can hardly be a spot on the entire boat with more vibration.

I reattached my cup with 4200, then placed a bead of LifeSeal around the base, inside and out.

Gordon

 

[GarryH]

Gordon, sounds good. Just an FYI, the transducer on my 2021 R2-29CB is mounted on the interior hull in the V berth on the starboard side between the bed and the make-up desk. I would think that hull area receives a lot of banging while underway. Not sure why the factory installed it there. In any event, hope your latest solution is successful.

 

[deanmyring]

Hey all. My transducer isn’t working. Located it under the starboard locks. BOY it’s a tight space. Any suggestions on tools etc ? It’s almost impossible to reach.