Lowrance lms-520c Operating Guide

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First find a location on the boat's transom where the water flow is 

smoothest. Don't mount the sensor behind strakes or ribs. These will 

disturb the water flow to the speed sensor. Make sure the sensor will 

remain in the water when the boat is on plane. Also make sure the lo-

cation doesn't interfere with the boat's trailer. Typically, the sensor is 

mounted about one foot to the side of the transom's centerline. 
Once you've determined the proper location for the unit, place the sen-

sor on the transom. The bottom of the bracket should be flush with the 

hull's bottom. Using the sensor as a template, mark the hull for the 

screws' pilot holes. Drill four 1/8" holes, one in each end of the slots. 

Mount the sensor to the hull using #8 stainless steel wood screws (not 
included). Use a high quality, marine grade above- or below-waterline 

sealant to seal the screws. Make sure the sensor is flush with the bot-

tom of the hull and tighten the screws. 

 

   

 

If the base of the transom has a radius, fill the gap between the tran-

som and the sensor with the sealant. This will help ensure a smooth 

water flow. 

Route the sensor's cable through or over the transom to the sonar unit. 

If you need to drill a hole in the transom to pass the connector through, 

the required hole size is 7/8".