A sandwich hull also requires polyester resin. Selecting a Transducer Location 1. The location must be in the water at all times, at all operating speeds. 2. The transducer must be placed in a location that has a smooth flow of water at all times. If the transducer is not placed in a smooth flow of water, interference caused by bubbles and turbulence will show on the sonar's display in the form of random lines or dots whenever the boat is moving. NOTE: Some aluminum boats with strakes or ribs on the outside of the hull create large amounts of turbulence at high speed. These boats typically have large outboard motors capable of propelling the boat at speeds faster than 35 mph. Typically, a good transom location on aluminum boats is between the ribs closest to the engine. 3. The transducer should be installed with its face pointing straight down, if possible. For shoot-thru applications: Many popular fishing boat hulls have a flat keel pad that offers a good mounting surface. On vee hulls, try to place the transducer where the deadrise is 10° or less. Deadrise less than 10° Pad Strakes Left, vee pad hull; right, vee hull. A pod style transducer is shown here, but the principle is the same for Skimmers inside a hull. 4. If the transducer is mounted on the transom, make sure it doesn't interfere with the trailer or hauling of the boat. Also, don't mount it 9 closer than approximately one foot from the engine's lower unit. This will prevent cavitation (bubble) interference with propeller operation. 5. If possible, route the transducer cable away from other wiring on the boat. Electrical noise from engine wiring, bilge pumps and aerators can be displayed on the sonar's screen. Use caution when routing the transducer cable around these wires. CAUTION: Clamp the transducer cable to transom near the transducer. This will help prevent the transducer from entering the boat if it is knocked off at high speed. Good location Poor location Good location Good location Poor angle Good and poor transducer locations. How low should you go? For most situations, you should install your Skimmer transducer so that its centerline is level with the bottom of the boat hull. This will usually give you the best combination of smooth water flow and protection from bangs and bumps. 10 TransomTransom Hull bottomHull bottom Transducer centerline TransomTransom Hull bottomHull bottom Transducer centerline Align transducer centerline with hull bottom. A dual frequency transducer is shown at left and a single frequency transducer at right. However, there are times when you may need to adjust the transducer slightly higher or lower. (The slots in the mounting brackets allow you to loosen the screws and slide the transducer up or down.) If you frequently lose bottom signal lock while running at high speed, the transducer may be coming out of the water as you cross waves or wakes. Move the transducer a little lower to help prevent this. If you cruise or fish around lots of structure and cover, your transducer may be frequently kicking up from object strikes. If you wish, you may move the transducer a little higher for more protection. There are two extremes you should avoid. Never let the edge of the mounting bracket extend below the bottom of the hull. Never let the bottom – the face – of the transducer rise above the bottom of the hull. Shoot-Thru-Hull vs. Transom Mounting In a shoot-thru-hull installation, the transducer is bonded to the inside of the hull with epoxy. The sonar "ping" signal actually passes through the hull and into the water. This differs from a bolt-thru-hull installation (often called simply "thru-hull"). In that case, a hole is cut in the hull and a specially designed transducer is mounted through the hull with a threaded shaft and nut. This puts the transducer in direct contact with the water. 11 Typically, shoot-thru-hull installations give excellent high speed operation and good to excellent depth capability. There is no possibility of transducer damage from floating objects, as there is with a transom- mounted transducer. A transducer mounted inside the hull can't be knocked off when docking or loading on a trailer. However, the shoot-thru-hull installation does have its drawbacks. First, some loss of sensitivity does occur, even on the best hulls. This varies from hull to hull, even from different installations on the same hull. This is caused by differences in hull lay-up and construction. Second, the transducer angle cannot be adjusted for the best fish arches on your sonar display. Lack of angle adjustment can be particularly troublesome on hulls that sit with the bow high when at rest or at slow trolling speeds. Third, a transducer CAN NOT shoot through wood and metal hulls. Those hulls require either a transom mount or a thru-hull installation. Fourth, if your Skimmer transducer has a built in temp sensor, it will only show the temperature of the bilge, not the water surface temp. Follow the testing procedures ...