Outboard Thermostats & Temperature Senders

A coolant temperature sender is an on engine protection device that is used to monitor the coolant temperature of the engine. A thermostat is a valve in the outboard's cooling system that opens or closes depending on temperature.

Mercury outboard thermostat. Yamaha outboard thermostat. A thermostat is designed to hold the cooling water in the block until it reaches the temperature set by the engine manufacturer. A thermostat regulates the temperature of the water for engine cooling and keeps pressure in the cooling system to facilitate heat transfer Boat thermostats are an integral part of your marine engine and should not be overlooked when completing your routine maintenance. These devices regulate the temperature of the water used in cooling your boat's engine. The coolant temperature sensor, also known as the coolant temperature switch, is an engine management system sensor that is used to monitor the temperature of the engine's coolant. Most coolant temperature sensors operate using electrical resistance to measure the temperature of the coolant. The cooling system on an outboard is a very simple and compact application. Water is inducted through the lower unit by a water pump impeller, and then forced upward to circulate throughout the powerhead, and eventually exits through the exhaust system. The function of the thermostat is to control the flow of cooling water through the engine. The temperature sending unit, more properly known as a temperature sensor, is one of the most important sensors in your car. It is the sensor that tells the computer when the engine has warmed up sufficiently for the computer to pay attention to the many other sensors on the engine and exhaust. The thermostat is a valve that regulates the operating temperature of the outboard by opening to let cool water flow through the engine, and closing to prevent the flow of water from inhibiting the engine's ability to reach its ideal operating temperature. The thermostat on most Mercury outboards should be inspected annually or every 100 hours. It's a task that usually can be done along with the 100-hour oil-and-filter and gearcase lube change, or when offseason layup is performed. The water temperature sender is designed to measure the integrity of the engine cooling system. The sender responds to changes in engine coolant temperature, displayed via operation of the water temperature light or gauge. thermostats should be serviced every two to three years. This varies on where you do most of your boating. When the thermostat is closed, it prevents the flow of cooling water passing through the outboard, thus increasing the motor's operating temperature. As the temperature rises, the thermostat opens and allows coolant to flow through the outboard, thus decreasing its operating temperature. you can temporarily run your outboard without the thermostat and not harm the engine. Your boat's water temperature gauge provides important information about your engine. The gauge indicates your engine operating temperature and tells you whether the engine is in danger of overheating.