Which gear oil type should be used at the specified areas in a lower unit assembly?

The appropriate choice for gear oil in a lower unit assembly is standard gear oil. This type of oil is specifically formulated to provide the necessary lubrication and protection for the gears and components within the lower unit. Standard gear oil has the right balance of viscosity and additives to minimize wear and resist breakdown under the demanding conditions of marine environments, such as water exposure and varying temperatures.

Using standard gear oil ensures optimal performance and longevity of the lower unit assembly by preventing metal-to-metal contact, reducing friction, and providing a cushioning effect between moving parts. This oil type also helps in sealing the assembly against water ingress, which is critical for maintaining the integrity of the lubricated components.

In contrast, high viscosity oil may not flow appropriately in the system, especially at lower temperatures, leading to inadequate lubrication. Low viscosity oil might be too thin to offer sufficient protection under heavy load conditions typical in marine environments. Water-based oil is not suitable for gear systems as it lacks the necessary lubricating properties and can result in corrosion and component failure. Thus, standard gear oil is the best choice for ensuring the reliability and performance of the lower unit assembly.