I remember the first time I bought a Mercury outboard — I had no idea I was supposed to flush it after running in saltwater. A buddy of mine set me straight, and since then it’s become part of my post-trip ritual. Here’s exactly how I flush mine at home with nothing more than a garden hose.
- Hook Up the Muffs
I use a standard set of “ear muffs” that clamp over the lower unit water intake. They look like two rubber cups connected by a metal spring. I slide them snugly over the intakes and make sure the hose connection is tight. - Turn On the Water First
This is critical — always get water flowing before you start the engine. I turn the hose on about halfway, just enough to see water spraying out both sides of the muffs. - Start the Outboard
Once the water’s flowing, I fire up the Mercury. Within a few seconds, I look for a steady stream coming out of the telltale (the little “pee hole”). If it’s weak, I jiggle the muffs until it’s strong. - Let It Run
I usually let mine run for 10 minutes. That’s enough to flush out the salt, sand, and muck. While it’s running, I’ll often check the prop or do a quick walkaround of the boat. - Shut Down Safely
I always turn the engine off first, then the hose. That way the pump never runs dry.
It’s simple, but doing this religiously has saved me from a lot of overheating and clogged water passages. If you run your Mercury in brackish or saltwater, flushing is a must