Flushing Out Your Boat's Engine Block: A Step-By-Step Guide

Flushing out a boat's engine block is an essential part of boat maintenance, especially for saltwater vessels. Salt and other minerals can cause corrosive build-up, which can block the dissipation of heat and lead to engine overheating, fires, and engine failure. To prevent this, boat owners should regularly flush out their engine blocks, using either freshwater or a de-salt solution. This process involves running water through the engine's cooling system, either with the engine on or off, depending on the method and engine type. This simple but crucial task helps to ensure the boat's performance and durability.

Flushing with a de-salt concentrate

Flushing your boat's engine with a de-salt concentrate is a great way to prevent salt corrosion and maintain the integrity of your boat's engine. Saltwater is highly corrosive, and if you use your boat in saltwater, you should ideally flush the salt out after every use.

The Process

Once you have your de-salt concentrate, follow these steps:

• Connect a garden hose to your boat's engine. Most modern outboard engines have a flushing connection on the side, which makes this process simple. If you have an inboard engine, you may need to use a flush kit with "muffs" to cover the intake holes and ensure water from the hose makes it into the engine without sucking in air.
• Turn on the water supply and allow fresh water to run through the engine's cooling system for several minutes.
• Check for proper water outflow. Observe the water exiting the exhaust port connected to the exhaust manifold. If the flow is steady and clear, your flush was successful.
• Optional: For an extra layer of protection, you can use a de-salt concentrate product like Better Boat's. Fill the dispenser bottle that comes with the flush kit with the concentrate.
• Turn the valve to the "mix" setting to dispense the de-salt solution along with the water. Run the engine until it reaches operating temperature, then change it back to the "mix" setting to flush the engine with the de-salt solution.
• Continue flushing the engine until the canister is clear. This will leave a protective coating on the engine, which will keep it protected while it's not in use or during the beginning of your next trip.

Benefits of Flushing with a De-Salt Concentrate

• Improved Engine Performance: Regular flushing with a de-salt concentrate will help improve engine performance by removing salt buildup and preventing corrosion.
• Extended Engine Life: Salt corrosion is a major factor in reducing the lifespan of boat engines. By regularly flushing with a de-salt concentrate, you can extend the life of your engine.
• Peace of Mind: Knowing that your boat's engine is well-maintained and protected against salt corrosion will give you peace of mind and help you sleep better at night!

Flushing with fresh water

To flush your boat engine with fresh water, you will need a garden hose that can reach your boat and provide an adequate water flow. A 1-1/4 inch diameter hose is typically recommended. You will also need to consult your owner's manual to locate the cooling system components, such as the raw water intake and flushing valve, and to determine how to connect the hose to your boat.

Once you have located the cooling system components and connected the hose, you can begin running fresh water through the engine's cooling system. It is standard practice to start with a low level of water flow and slowly increase it. Allow the water to flow through the hose and into the engine for several minutes.

After flushing, it is important to check for proper water outflow. Observe the water exiting the exhaust port, which is connected to the exhaust manifold. If the flow is steady and clear, you can be confident that the flushing process was successful.

It is recommended to flush your engine for at least 5-10 minutes after each use. It is also important to note that you should never flush a hot engine, as it can cause damage from thermal shock. Always allow the engine to cool before flushing.

Flushing with antifreeze

Flushing your boat engine with antifreeze is a crucial step in winterizing your boat to prevent costly repairs and extend the life of your engine. Antifreeze is used to prevent residual water from freezing and cracking your engine block as it expands.

Types of Antifreeze

There are two types of antifreeze: automotive antifreeze and non-toxic antifreeze. Automotive antifreeze, such as Prestone, is suitable for cars and boats with a closed, freshwater cooling system. However, most boats have a raw water cooling system, so a non-toxic variety is recommended to ensure safety as it can be used and disposed of more safely. This type of antifreeze is made from propylene glycol and often contains corrosion inhibitors to protect the engine and cooling system.

Choosing the Right Concentration

When selecting the concentration of antifreeze, opt for the highest concentration available, typically -100°F. This is because there is usually some residual water inside the engine, which dilutes the antifreeze. A higher concentration ensures that the resulting freezing point remains low enough to prevent freezing.

Steps for Sterndrives

If your boat is a sterndrive, you can use a winterizing kit to simplify the process. First, connect a garden hose to a faucet and then to a motor flusher, placing it over the raw water intake. Turn on the freshwater and start your boat's engine, allowing it to warm up to operating temperature so that the thermostat opens and coolant circulates throughout the engine.

Next, turn off the engine and attach the winterizing kit to the motor flusher. Remove the flame arrestor from the carburetor. Start the engine again and open the valve to the tank of the winterizing kit, allowing the antifreeze to circulate through the engine.

Once the tank is nearly empty, begin spraying fogging oil into the carburetor. This will typically cause lower-horsepower engines to stall, while higher-horsepower engines may continue running with white smoke. Spray a sufficient amount and then turn off the engine. Alternatively, you can remove the spark plugs and spray the fogging oil directly into each combustion chamber.

Steps for Inboard Engines

For inboard engines, you will need a five-gallon bucket filled with undiluted non-toxic antifreeze. If your boat is in the water, close the intake seacock. Remove the raw water intake hose from the seacock and insert it into the antifreeze in the bucket.

Start the engine and run it at idle until antifreeze discharges from the exhaust outlet for at least 30 seconds. When the bucket is almost empty, begin fogging the carburetor with fogging oil. Spray a generous amount while the engine is running, and then turn off the ignition. Finally, secure the intake hose back onto the seacock.

Additional Tips

It is important to note that antifreeze should be flushed out of the system in the spring to ensure proper functioning during the boating season. Additionally, always refer to your engine's owner's manual or service manual for specific instructions, as different engines may have unique winterizing requirements.

Flushing with the engine running

• Quick-connect a water hose to the Easy Flow Valve. Ensure the engine is not running at this point.
• Water will pass from the valve through a tee, then to the water pump, where it will momentarily stop.
• Due to the path of least resistance, the water will vent back from the tee and out through the out-drive vents, thoroughly flushing the out-drive. These vents prevent the over-pressurization of water to the water pump.
• With the engine running and the thermostat open, the water will be pumped through the rest of the circulation system.
• The seal-proof water inlet and the instant flow of pressurized water to the water pump enable the pump to circulate the maximum amount of water through the circulation system.
• With the water turned on fully, the oversupply of pressurized water to the tee blocks off the passageway to the out-drive, preventing air from being sucked in through the intake vents.
• You will know there is an oversupply of water to the water pump when you notice more water than usual coming out of the exhaust during flushing.
• After flushing, quickly and securely seal the valve inlet with the quick-connect cap, allowing the boat's circulation system to function as usual.

It is important to note that the engine must be heated so that the thermostat is open to flush the entire system. Additionally, always refer to your boat's specifications before installing any new system, as certain setups may not be compatible with the Easy Flow System.

By following these steps and using the Easy Flow System, you can effectively flush your boat engine with the engine running, ensuring a thorough cleaning of the water pump's impeller and housing.

Flushing without the engine running

Flushing your boat engine without running it is possible and is sometimes preferable. For example, if you've returned home late, or you're in a caravan park where the noise of running the engines is an issue, flushing without running the engine is better than not doing it at all. However, you will still need to give it a proper flush as soon as you can.

Step 1: Prepare the Engine

Before you begin flushing, you need to prepare the engine. This includes removing the boat from the water and locating it near a freshwater hose port. If your engine has a flushing port, tilt the engine up until the outdrive has drained, and remove the cap of the flushing port. If your engine does not have a flushing port, you will need to purchase a pair of flushing muffs or earmuffs, which are used to flush the system with freshwater.

Step 2: Attach the Hose

The next step is to attach the hose to the engine. If your engine has a flushing port, simply attach the hose to the flushing port. If your engine does not have a flushing port, attach the hose to the flushing muffs or earmuffs, and then slip the muffs over the tail motor, fully covering the water intakes. Make sure that the water is flowing around both sides of the intake spots.

Step 3: Turn on the Freshwater Source

Turn on the freshwater source and let it run for 3-5 minutes. Ensure that the water is flowing through the tell-tale, which is connected to the exhaust manifold. If your engine does not have a tell-tale, you can check for proper water outflow by observing the water exiting the exhaust port. If the flow is steady and clear, you can be confident that the flushing process was successful.

Step 4: Turn off the Freshwater Source and Remove Attachments

Once the engine has been flushed with freshwater for 3-5 minutes, turn off the freshwater source and remove the hose and any other attachments, such as the flushing muffs or earmuffs.

It is important to note that if you have more than two intakes on the gear case, you will need to cover them with tape to seal them to prevent overheating. Additionally, if your motor is old and does not have any intakes on the gear case, you will need to purchase a flushing bag.

By following these steps, you can effectively flush your boat engine without running it, helping to prevent salt build-ups and corrosion, and ensuring the optimal performance and longevity of your engine.

Frequently asked questions