Methods and systems are provided for maintaining a desired engine coolant level and a relative glycol amount in the engine coolant by using water sourced from on-board vehicle systems. In one example, a method may include supplying water to the engine coolant reservoir in response to the engine coolant level decreasing below a threshold. Also, a relative glycol amount in the coolant may be maintained at a threshold amount by adding water to the coolant in response to a relative glycol increasing above the threshold.

Methods and systems are provided for maintaining a desired engine coolant level and a relative glycol amount in the engine coolant by using water sourced from on-board vehicle systems. In one example, a method may include supplying water to the engine coolant reservoir in response to the engine coolant level decreasing below a threshold. Also, a relative glycol amount in the coolant may be maintained at a threshold amount by adding water to the coolant in response to a relative glycol increasing above the threshold.

Methods and systems are provided for maintaining a desired engine coolant level and a relative glycol amount in the engine coolant by using water sourced from on-board vehicle systems. In one example, a method may include supplying water to the engine coolant reservoir in response to the engine coolant level decreasing below a threshold. Also, a relative glycol amount in the coolant may be maintained at a threshold amount by adding water to the coolant in response to a relative glycol increasing above the threshold.

An outboard motor unit includes an outboard motor including a cowling and an engine housed in the cowling and that is mounted on a vessel body, a supercharger that compresses air, and a compressed air cooler that is installed outside the cowling of the outboard motor and cools air compressed by the supercharger.

An outboard motor unit includes an outboard motor including a cowling and an engine housed in the cowling and that is mounted on a vessel body, a supercharger that compresses air, and a compressed air cooler that is installed outside the cowling of the outboard motor and cools air compressed by the supercharger.

A marine vessel includes a cooling flow passage to allow cooling water to flow into a cylinder block from a lower side of the cylinder block via a lower end flow passage port in a vicinity of or adjacent to a lower end of a flow passage portion in the cylinder block.