Powerboats
Watercraft Engine Maintenance

Why do you need to flush 9.9HP mercury outboard?

User Avatar
Wiki User
May 26, 2009 6:24PM

The motor has an intake that sucks water in to keep the engine cool and then shoots it out. Much like a car but a car has a closed system. Some boats have closed systems also especially if they are used in salt watwer as salt water is corrosive. Hope this helps...