Understanding Yanmar Engine Gearbox Temperature Control

Yanmar marine gears are essential for transmitting power from the engine to the propeller, ensuring smooth transitions between neutral and engaged, and forward and reverse propeller rotation. While Yanmar provides specific recommendations for oils and coolants based on the engine model and drive/gear models, there is a range of temperatures that are considered normal for Yanmar engines. For example, the Yanmar YSB12 has a thermostat that opens at 115 degrees Fahrenheit, while engines with heat exchangers should operate at around 180 degrees Fahrenheit.

What oil should I use for my Yanmar engine and gearbox?

The oil you should use for your Yanmar engine and gearbox depends on the model of your engine and gearbox. It is recommended to refer to the Operation Manual for specific recommendations for your operating conditions or discuss with your local Yanmar dealer.

For example, the Yanmar 2GM20 (raw water version) specifies SAE 30 oil for the gearbox. However, the manual for the 4JHBE specifies Dextron II equivalent for the gearbox. The manual for the 3GM30F (which also covers the 2GM20) says to use API CC, SAE 10w-30 in the gearbox and SAE 20, 30 or 40 in the engine, depending on the temperature.

For the engine, the manual for the 2YM15 recommends API Service Categories: CD or higher, TBN value: 9 or more, and Recommended SAE Viscosity: 10W30,15W40. It is important to note that API Service Category CG-4 or CH-4 oils should not be used.

For the gearbox, the manual for the 2YM15 recommends API Service Categories: CD or higher, SAE Viscosity: #20 or #30. This refers to a single-weight oil, not a multi-grade oil like 10W30.

It is also worth noting that some sources suggest using the same oil for both the engine and gearbox. For example, the 1GM gearbox uses the same oil as the engine, and the Kanzaki KM2-A transmission specifies the use of the same oil as the engine, which is 30 wt. oil. However, it is always recommended to refer to the specific guidelines for your particular Yanmar model.

What temperature should a Yanmar engine be running at?

The ideal operating temperature for a Yanmar engine depends on the type of engine and the model. Yanmar marine gears are fundamental to the functioning of the vessel, transmitting power from the engine to the propeller.

Freshwater-cooled Yanmar engines typically operate at lower temperatures of around 120°F (48.9°C). This is because the parts in contact with seawater will accumulate less scale at lower temperatures. The thermostat for these engines often opens at 115°F (46.1°C).

On the other hand, Yanmar engines with heat exchangers should operate at higher temperatures, with an ideal range of 180°F (82.2°C) to 190°F (87.8°C).

For example, the opening temperature of the thermostat for the Yanmar 6LP DTE engine is 167°F-174°F (75°C-78.9°C), and the full-open temperature is 194°F (90°C).

It is important to note that running a Yanmar engine too hot can cause issues. A temperature above 190°F (87.8°C) is considered problematic and can lead to corrosion and scale buildup in the engine's cooling passages.

To ensure optimal performance and avoid potential issues, it is recommended to refer to the specific Operation Manual for your Yanmar engine model or consult with a local Yanmar dealer. They can provide guidance on the ideal operating temperatures and the appropriate oils and coolants for your particular engine.

What is the normal operating temperature for a 1980 Yanmar 2QM15?

The normal operating temperature for a 1980 Yanmar 2QM15 is between 160-170°F (71-76°C). This range is typical for raw seawater-cooled engines, which run at cooler temperatures than closed-cycle cooling systems to limit scale formation in the engine cooling passages.

After replacing the water pump, temperature gauge, sending unit, and flushing the entire engine, some owners have reported operating temperatures of around 140°F. However, it is important to note that running the engine at a higher temperature can lead to increased corrosion and scale buildup, which can cause overheating and require an engine flush with harsh chemicals to resolve.

To maintain optimal performance and engine longevity, it is recommended to refer to the official Yanmar service manual for your specific engine model and year. The manual will provide detailed instructions and specifications for maintaining the correct operating temperature.

It is worth noting that different Yanmar engines have varying operating temperatures. For example, the Yanmar YSB12 has a thermostat that opens at 115°F, while engines with heat exchangers should operate at around 180°F. Additionally, the opening temperature of the thermostat for the Yanmar 2QM20 is reported to be 160°F, with a full-open temperature of 194°F.

Therefore, it is essential to consult the specific guidelines for your 1980 Yanmar 2QM15 model to ensure accurate information regarding its normal operating temperature range.

What is the opening temperature of the thermostat?

The opening temperature of the thermostat in a Yanmar engine varies depending on the model. For example, the opening temperature of the thermostat in a Yanmar YSB12 engine is 115 degrees Fahrenheit, while the opening temperature of the thermostat in a Yanmar 2QM15 engine is 160-170 degrees Fahrenheit. The opening temperature of the thermostat in a Yanmar 6LP DTE engine is around 175 degrees Fahrenheit at a cruise of 3100 RPM, and a Yanmar 240 YAQN engine runs at around 140-160 degrees Fahrenheit at most speeds.

It is important to note that the ideal operating temperature for a diesel engine is typically around 140-160 degrees Fahrenheit, with some sources recommending a maximum temperature of 160 degrees Fahrenheit and others suggesting that temperatures up to 190 degrees Fahrenheit are acceptable. Running a diesel engine too cool can lead to carbon build-up and related problems, while running it too hot can cause corrosion and scale formation in the cooling passages. Therefore, it is crucial to maintain the proper operating temperature for your specific Yanmar engine model to ensure optimal performance and longevity.

What is the full open temperature of the thermostat?

The full open temperature of the thermostat for a Yanmar engine is 194 °Fahrenheit (87-90 °Celsius). This is the temperature at which the thermostat will open completely.

The opening temperature of the thermostat is between 167-174 °Fahrenheit (75-79 °Celsius). This is the temperature at which the thermostat will start to open.

It is important to note that the ideal operating temperature for a diesel engine is around 140-160 °Fahrenheit (60-71 °Celsius). Running a diesel engine at temperatures higher than 190 °Fahrenheit (88 °Celsius) can cause problems.

The temperature of a Yanmar engine can be affected by various factors, including engine load, propeller speed, and ambient temperature. It is recommended to refer to the official Yanmar service manual for specific operating temperature recommendations for your particular engine model.

Additionally, it is worth noting that different Yanmar engines may have different thermostat opening and full open temperatures, so it is always best to consult the specific manual for your engine for accurate information.

Frequently asked questions