The 4.3 Mercruiser engine is a popular inboard motor for boats. It is equipped with four drain plugs. Before boats are stowed away for the winter, they must undergo a process known as "winterization." This means that the engine is completely emptied, cleaned, and antifreeze is applied so that damage does not occur over the cold season. The drain plugs are used to empty the engine of fluids. If the engine is not properly drained, it may incur damage.
Ensure that your boat is as level as possible. This will ensure total drainage when you are unplugging your drain plugs.
Move to your engine and locate the cylinder block.
Locate the two blue drain plugs attached to it, one on the starboard and one on the port side. If you face the motor, one will be on the lower-right side of the block about midway back. The other will be on the left side of the block behind the front motor mount.
Locate your exhaust manifold. Follow the manifold to the very bottom.
Locate the two blue drain plugs attached to it, one on the starboard and one on the port side.