You can get away with changing your car oil every few thousand miles and skating by with the occasional visit to the mechanic.
Boats, however, require a higher degree of care. You need to be prepared to carry out preventive maintenance. Take a few steps now to prevent a lot of time, money, and headaches later.
An ill-maintained boat can quickly become a liability. (We encourage you to look over our Ultimate Guide to Boat Maintenance.)
One of the regular maintenance tasks of every boat owner is to regularly flush out your boat’s cooling system to remove salt, debris, and other foreign gunk.
Why Do I Need to Flush My Inboard Marine Engine?
Most boat engines use water to cool the engine. Outboard marine engines typically have intake valves on the outside of the engine, while inboard marine engines may have intake valves built into the hull.
While these intake valves do have a filter, particles, other debris, and other water-borne intruders can work their way into these intake valves. When this happens while out on the water, it’s not a big deal. That is, unless, you consistently fail to flush out your cooling system when you get back to shore, allowing muck to build up over time.
The very worst-case scenario is to have your cooling system suddenly blocked. In this case, your engine can overheat and even melt down – just like a car with no water in the radiator.
Saltwater boaters take note: Salt is corrosive, so if you’re using your boat on saltwater or estuarine water, you should – in the perfect world – flush the salt out after every single use. That may be an unrealistic goal, but the general sentiment is that if your boat regularly comes in contact with saltwater, you should flush your cooling system as regularly as possible.
How Often Do I Need to Flush Out My Inboard Engine?
Boats that stay in the water don’t need to be flushed out as often. Seems counterintuitive, right?
We noted the danger that salt can cause in terms of corrosion. This is compounded when there is air in the system, which allows some of the salt water to evaporate – leaving behind salt crystals. The combination of air and salt can corrode the system from the inside out.
So, when your boat stays in the water – and the system never fully flushes out – there’s less chance of air/evaporation in the cooling system.
Benefits of Flushing Out My Inboard Engine
Salt is the main enemy when it comes to flushing out the engine, but sand, grit, and microbiotic plants and critters can also build up in the system.
There are many good reasons to flush out your engine:
- Prevent internal corrosion from salt.
- Prevent foreign stuff from gunking up the lines.
- Avoid coolant system blockage or limited circulation.
- Improve engine performance.
- Prevent the need for repairs and replacements.
- Avoid having your engine overheat.
- Extend the life of your engine.
- Protect your investment.
- Prevent the engine block from freezing/cracking in sub-zero storage.
When It’s Absolutely Necessary to Flush Out Your Inboard Boat Engine
Any time your boat is going into storage, it’s essential that you flush out the cooling system. Any salt in the system can cause corrosion. Note that this corrosion process begins almost immediately, so there’s no time to waste.
If you store your boat in sub-zero temperatures, failing to use an antifreeze coolant could result in freeze-related damage to your engine. Check out our guide: How to Winterize Your Boat.
And because you don’t want to pull a boat out of storage and find last season’s crud and muck, here’s our article about How to Clean a Boat: A Step-By-Step Guide to Thorough Boat Cleaning.
Tools You Need to Flush Your Inboard Engine
If this is your first time flushing the inboard engine on a particular vessel, you’ll want to consult the owner’s manual. It will indicate how to find all of the intake valves.
You’ll also need a garden hose that can reach your boat, in addition to a freshwater source and appropriate valve adapters. The garden hose will connect your engine to the freshwater source, while valve adapters will help you establish a secure connection between the hose and the engine’s cooling system.
Garden Hose
A garden hose plays a vital role in connecting your inboard boat engine to a freshwater source. When choosing a garden hose for this purpose, a 1-1/4 inch diameter hose is typically recommended, as it provides adequate water flow for effective flushing.
Standard practice is to start with a low level of water flow, and slowly increase the amount.
In terms of how to connect the hose to your boat, you’ll need to consult your owner’s manual, as the input valves are different on each vessel.
Flush Kits
Flush kits have two purposes. First, they provide valve attachments for different types of inboard and outboard motors. Second, some provide an additional solution for cleaning out your engine.
Some flush kits advertise additive solutions to remove salt. But do they actually help? You’ll have to test them yourself.
Salt naturally dissolves into fresh water, so it’s unclear if these are necessary.
But what we do know is that crustaceans like to colonize boats – most obviously in the case of barnacles and oysters. But all sorts of microbiota (plants and animals invisible to the eye) can slip through the filter on the intake valve. For these critters, some flush kits offer a biocide additive.
Usually, fresh water is sufficient to clean out your cooling system. Note: the additional additives marketed with certain flush kits won’t hurt your system, but we haven’t tested them and can’t say for certain how well they work.
Step-by-Step Guide to Flushing an Inboard Boat Engine
Now that you have the necessary tools and supplies, it’s time to begin the flushing process. This step-by-step guide will walk you through the process of:
- Locating cooling system components
- Connecting the hose
- Running water through the system
- Checking for proper flow
Following these steps facilitates effective flushing of your inboard boat engine, contributing to its optimal performance and longevity.
1. Locate the Cooling System Components
The first step in flushing your inboard boat engine is to locate the cooling system components, such as the raw water intake and flushing valve. You can find these components by consulting your owner’s manual.
2. Connect the Hose
Every boat has unique intake valves. The owner’s manual will tell you how to locate them and connect them to your hose. You may need additional attachments from a flush kit to marry the hose to the intake valve.
3. Run Water Through the System
Now that the hose is connected, you can begin running fresh water through the engine’s cooling system. Turn on the water supply, and allow the water to flow through the hose and into the engine for several minutes.
4. Check for Proper Water Outflow
You can assess the water flow by observing 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.
Tips for Effective Inboard Engine Flushing
How Long Should I Flush for?
As a general rule of thumb, it is advisable to flush your engine for 10 minutes after each use.
Can I Flush a Hot Engine?
No. Flushing a hot engine is a bad idea.
It’s important to flush your engine when it is cool to avoid damage from thermal shock. Running cold water through a hot engine can cause its components to contract rapidly, leading to cracking and potential damage.
Always Flush Prior to Storing Your Boat
Flushing is also necessary if you are storing your boat for any length of time. In fact, where and how your boat is stored is just as crucial to optimal boat health as maintenance procedures like flushing.
If you need help storing your boat, Neighbor has you covered with local, convenient places where you can rent a safe place to store your boat. The combination of preventive maintenance and good storage will significantly extend the life, performance, and value of your boat.
