Add Years to the Life of Your OutBoard with Fresh Water Flushing
Most of us take good care of our marine equipment. We wash and wax our boats and outboards, change the oil and oil filter regularly, and replace the fuel filters, but what about your outboard’s cooling system. Unfortunately, it is often overlooked in a maintenance regimen.
During the course of normal use, the water pump can ingest mud, sand, and silt, which then flows through the engine. Marine growth can also occur behind the inlet screens interrupting the flow of water to the engine. Over time, this debris can accumulate in the outboard’s cooling passages. It can also damage the water pump’s rubber impeller and plastic housing, eventually restricting the amount of water available to the engine. This can result in poor cooling, which will damage the engine and even promote corrosion in the exhaust system because of increased exhaust temperatures with today’s ethanol blended fuels and larger horse-powered outboards.
Source: (Baret News Wire / Sportsmans Life)
Here are some general facts about freshwater flushing. The outboard should be flushed after every use in salt or dirty water. Freshwater flushing with clean water will dislodge most contaminants (sand, silt, mud, etc.) and force them out of the passages in the cooling system. Perhaps even more importantly, flushing removes salt buildup, which can lead to poor cooling as well as corrosion of the engine block and midsection.
Generically speaking, there are three ways to flush an outboard: using a flush bag, flush muffs or the freshwater flushing attachment built into the outboard:
Flush Bag
- A flush bag is a sturdy collapsible bag that fits under the lower unit of the outboard and fills with water.
- By submerging the gearcase, it allows the motor to take in cooling water from the inlet screens and return it to the bag through the propeller.
- It requires running the engine (but only after the bag is filled with water).
- This can be done with the boat on a trailer or with the boat moored.
- Trim the outboard to the vertical position.
- Remove the propeller.
- Screw the garden hose into the connector on the bag and fill the bag.
- Make sure water level is approximately 5 inches above the anti-ventilation plate. This will assure that the water pump is completely submerged.
- Start the outboard and set the throttle to no more than a fast idle (800-900 RPM max).
- Watch for water coming out of the pilot tube at the lower rear of the cowling. Run the engine for 10-15 minutes.
- Stop the engine and turn off the faucet.
- Never run the engine without cooling water. Turn the freshwater on before starting the engine, turn the water off after stopping the engine.
Flush Muffs
- Flush muffs are rubber cups that fit over the water inlet on the gearcase (one of the cups has a hose fitting).
- They require running the engine (but only after the garden hose is in place and water running).
- This is best done with the boat on a trailer, or a lift completely out of the water.
- Trim the outboard to the vertical position.
- Remove the propeller.
- Remove the water inlet screens. This will allow more water to reach the impeller. Yamaha outboards will not pull the water in.
- Screw the garden hose onto the flush muff connector.
- Place the flush muffs over the water inlets on gearcase.
- Turn the water on slowly, until you can see a bit of water leaking from around the flush muff rubber cups.
- Check to ensure the rubber cups are still in place over the inlets.
- Start the outboard and set the throttle to no more than a fast idle (800-900 RPM max).
- Watch for water coming out of the pilot tube at the lower rear of the cowling.
- There should be some water exiting the back of the gearcase, through the exhaust also.
- Run the engine for 10-15 minutes.
- Stop the engine and turn off the faucet.
- Never run the engine without cooling water. Turn the freshwater on before starting the engine, turn the water off after stopping the engine.
- Don’t rev the engine while using flush muffs, because there isn’t enough water flow/pressure to sufficiently cool the engine at high rpm.
- Running the outboard with little or no cooling water will cause expensive overheating damage in a very short time.
Built-In Flushing Device
- A built-in flushing device is a hose fitting, usually located near the lower rear cowling.
- Don’t run the engine during this procedure.
- An outboard can be flushed with the boat on a lift (or in the water, it works best if you can trim the engine up so the gearcase is out of the water).
- Connect a garden hose to the outboard’s flushing device fitting.
- Turn on the faucet; let freshwater run through the outboard for 10-15 minutes.
- Turn off the faucet; disconnect.
- Put the cap back on engine’s flush fitting (per owner’s manual).
Which Method is Best?
Using a flushing bag is the best method for flushing an outboard motor. Because they work with the engine running, flush bags and flush muffs allow the engine’s thermostat to open and water to enter passages in the cylinder head. (Running an outboard in a flush bag is also the best method for fogging an engine prior to winter storage.) If it is not practical to use a flush bag or flush muffs, then using the provided flush attachment is the preferred method. In all cases, regularly check to see that water inlet screens on the lower unit are clear and clean.
Flushing your outboard with freshwater on a regular basis can go a long way toward extending the outboard’s life span – especially for those who boat in saltwater. Freshwater flushing is easy and cheap, so keep the garden hose handy.
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