After the trip to Lake Huron last summer, the Datamarine Dart display aboard BEN MAIN, Jr. quit working. Checking with a repair facility, it was obvious that the display could not be repaired. The push button system wasn’t available for the repair. The speed, temperature, depth, and display would need to be replaced. PICK A NEW SYSTEM While at Strictly Sail in Chicago, I checked with a number of venders. The Navman system appeared to be a good replacement. They confirmed that the installation was possible. After talking with Tom Grimes, he decided on the Navman system as the replacement. It offered the same basic features as the old system plus some new ones. The best feature was the ability to display both speed and depth at the same time. No more jumping from one screen to another as required with the Datamarine Dart display.
The old Datamarine display required a little force to break the Instrument free from the adhesive. Photo: Tom Davison© 2005
The transducers in the standard Navman box would not fit. The twoinch holes from the Datamarine system were the larger than the standard Navman through-hulls. A special order was required. The transducers would hopefully match and fit into the existing holes in the hull. While the dimensions appeared to be identical, we would need to get the parts to confirm the fit. The display had a similar size to the Dart, but the hole through the cabin wall was smaller. More on that later. EQUIPMENT REMOVAL The first task was to take out the old equipment. Two of the three items of the old Datamarine system were not difficult to remove, but the depth transducer took a little longer and more force. Looking back, this was an easy task. Working around holes in the hull make me nervous.
The display hole is through the gelcoat, fiberglass, marine plywood and the interior teak surface. Photo: Tom Davison© 2005 Aboard BEN MAIN, Jr. Take Out the Display The Dart display aboard BEN MAIN, Jr. was located on the port side of the cabin. This single display had four functions: depth, speed, distance log, and water temperature. The keypad got lots of use. The thin clear plastic layer protecting the instrument finally cracked allowing moisture to enter. The display was behind a teak box. It was held in place by a simple u-shaped bracket, secured by two nuts and adhesive was used to seal the hole through the cabin. Removal was simple; take the cover off, remove the bolts and wires, then apply enough pressure on the back of the instrument to break the adhesive free. While this wasn’t difficult, the adhesive was determined to hold the display in place. The speed sensor through-hull is located under the starboard seat and shares the space with the grounding system. Photo: Tom Davison© 2005
Speed/Log/Temp The speed / log / temperature sensor is located under the starboard seat across from the galley, forward of the head. The speed/log sensor has a through-hull fitting and it slides into the fitting from the interior of the boat. It is sealed with two o-rings and held in placed by the clevis pin and ring. There is a plastic plug to replace the sensor that can be used while the boat is in the water. Depth The depth transducer is located beneath the sink. This installation was different than the speed sensor. Instead of a tube that held the sensor, the depth transducer was one piece. It went through the hull and was held in place by a large nylon wing nut.
With the application of some direct force, the old Datamarine through-hull separated from the hull. Photo: Tom Davison© 2005
There were two teak pieces to adjust the angle of the transducer to vertical. The shape when viewed from below was like a football. This allowed water to flow around the transducer. The smaller teak piece was placed on the interior of the hull and the large one was on the outside. Replacing the Navigation Instruments The most difficult removal was the depth transducer. It was also held in place by sealant and a locking ring. This seal required additional force and a short piece of PVC pipe of the correct diameter was used to force the transducer free while doing no damage. Hitting the plastic with a hammer makes you nervous. With a couple of good hits, the through-holes broke free and could be pushed out of the hull After the removal, the hull thickness was measured and found to be roughly 20 mm. This made me feel a bit better about using a hammer on a Flicka. Cables and Wires The next step was to remove the teak piece used to hide the wires leading to the display. Three small wood screws and the wires are uncovered. The depth finder cable runs aft along the hull through a hole in the liner. After passing through the hole into the engine compartment, the wires ascend to the port berth. They wrap around the aft wall of the cabin to a hole just above the berth.
The depth transducer is located beneath the sink on the port side of the hull. A nylon wing nut and adhesive hold it in place. Photo: Tom Davison© 2005
The cable for the speed log follows a similar path on the starboard side of the Flicka. Besides crossing the engine area, the hole in the hull liner is shared with the diesel fuel lines. The power wire leaves the switch panel and descends to the edge of the teak. There was a simple change here. All of the wires meet and pass through a small hole in the teak wall just above the quarterberth. From this point the wires ascend to the back of the display. The wires are hidden from view by the piece of long narrow piece of teak. A slot was cut into the wood to give it a wide u-shape, with just enough room for two cables and one wire. The extra cable length for both transducers is wound in a coil and secured with wire ties in the bottom of the liner.
After knocking the depthfinder loose, it was removed. The Datamarine transducer was one piece. The new Navman transducer would fit inside of a through-hull allowing removal while in the water. Photo: Tom Davison © 2005 Aboard BEN MAIN, Jr. ORDERING NEW EQUIPMENT With the old display and transducers out, their exact measurements could be determined and the final ordering was done. This raised the cost of the system. The speed/log/temp transducer might be the same size as the standard navigation package, at two inches. The standard depth transducer was smaller and would not work. A special order was necessary to obtain one that would fill the hole in the Flicka hull. The speed sensor was also a smaller diameter, but an adapter would allow use of their two-inch through-hull. The order was placed and shipping was arranged to a local marine store. Make sure you get the four pin to eight pin adapter!
The new Navman speed / temperature sensor, through-hull, reducing adaptor, plug, washer and nut. The adapter has a flap that closes when the sensor is removed thus keeping water out. The plug is in the center of the photo. Photo: Tom Davison© 2005
The new Navman depth finder allows the transducer to be removed without removing the through hull. This is definitely an upgrade. Photo: Tom Davison© 2005
INSTALLING NEW EQUIPMENT After seven days, the package arrived and it was time to examine the new items and begin installation. Display Of the three primary pieces, the display was the part least similar to the old equipment. The Datamarine Dart display had a slightly smaller face, but the hole through the cabin wall was two inches which was larger than the new display. The problem was solved with a piece of aluminum that would act as a very large washer. The nylon washer supplied with the display barely fits the threads. It was trimmed and reversed to allow full contact with the threads of the display. Speed / Log / Temp The new Navman System had three parts. There is the through-hull, the speed / temperature sensor and an adapter to take up the space between these two different diameters. The adapter is unique (and patent-pending). It has a small tensioned flap inside. When you remove the transducer, the flat closes and helps prevent water from entering the hull. After checking the fit, Boatlife sealant was applied and the new through-hull was installed. Replacing the Navigation Instruments Depth After removing the old adhesive, the new transducer was dry fitted into the teak and placed in the hull. Everything lined up perfectly the first time. The next step was to remove everything and add the sealant. This would provide a good seal, remain flexible and allow for future removal in the event of failure or another upgrade. Sensor Cables The cable runs are not far, but they do wind around other hoses and wires before reaching the through-hulls. You should wait until everything is working correctly to secure all the wire runs with wire ties or to cover the display. Everything can be hidden once you confirm that the system works. Power Cable The cable from the display ended in seven wires, all tinned. They provided power, ground, NMEA In/Out. Two small plastic computer wire fittings were obtained from Radio Shack. The fittings are for small computer wiring and allow removal of the display without cutting the wires.
The depthfinder through-hull passed through a wood puck, which is sealed to the bottom of the hull. Being able to remove the transducer is an improvement over the old Datamarine system. Photo: Tom Davison© 2005
Power had been delivered via a small fuse holder behind the switch panel. While behind the electrical panel, the battery and shore power were disconnected. An electrical meter was used to confirm that all power was gone before working on the electrical wires. To replace this fuse would mean removing the face of the switch panel, changing the fuse and then putting the panel back in place. The fuse was moved to a location behind the aft wall of the cabin, directly above the quarterberth. It was secured out of the way using wire ties. Launching With the instruments in place and the curing time past, it was time to test the installation. BEN MAIN, Jr. was launched in the morning. The seals were good, no water entered the hull.
The new Navman speed / temperature sensor through-hull, reducing adaptor, plug, washer and nut. Photo: Tom Davison© 2005 Aboard BEN MAIN, Jr. Speed Trials Now that the new instruments were in place, it was time to test the operation. We checked their performance under power and sail. The depthfinder worked very well. While the temperature portion of the sensor was working well, the speed information functions appeared to be dead on arrival. Time to call the manufacturer. Navman gave Tom instructions for the return of the speed sensor and asked that the display also be sent. The display was removed and the old Datamarine display was reinstalled to keep the cabin watertight. The speed sensor plug was used to seal the hull. They promised a fifteen working day return or three weeks total with shipping. The new Navman display covered the hole through the cabin. An aluminum washer was fabricated to hold the instrument beneath the nylon retaining nut. Photo: Tom Davison© 2005
Two weeks later, a package arrived from Navman. The display and speed sensor were reinstalled. Time for another trial. A Garmin 76 G.P.S. was used to check the speed. It was more difficult to calibrate the speed up wind since the G.P.S. lagged behind the speed of the display. Downwind was easier since the speed remained more constant. The Navman recommendation that the calibration be adjusted above five knots presented some trouble. We didn’t have the wind to go that fast, or a cruising genoa to power to the desired speed. Still, we were able to determine a difference. The calibration was easy using the display keypad. With everything working, the cables and wired were secured with wire ties and the teak was replaced. The teak box hiding the display was cut down from five inches to just two.
The new Navman display is ready to go. The ability to see the depth and boat speed at the same time may be the best new feature. Photo: Tom Davison© 2005
All in all, the installation was straightforward. If the display worked from the start, this would have been a 1-2-3 installation. The system has worked well since the second installation.