After your boat’s spent months in winter storage, you’ll be eager to get back out on the water once boating season arrives.
But before you plan your first day on the water, you’ll need to test your inboard boat engine while still on dry land. This step is an important piece of regular maintenance for boat owners. It’s easier to diagnose engine problems on land, where you can see what’s coming out of the engine by monitoring the exhaust.
The challenge is that inboard engines need water to self-cool. (An outboard motor is also — typically speaking —water-cooled, though it requires different equipment called “ear muffs” to test. For this article, we’ll focus on inboard engines only.)
So, how do you test your engine before you enter the water? Read on, and we’ll show you how to use an inboard water flusher.
Flushing Your Inboard Engine With Water
To test your inboard on land, you have to “fool” your boat into thinking it’s in a body of water. This is accomplished using an inboard water flusher – also known as a fake-a-lake device (like this one).
Testing your inboard engine on land is especially important when de-winterizing your boat but is also recommended when bringing your boat out of storage. (If you’re unfamiliar with dewinterizing or storage considerations, check out our Boat Winterization Guide and Quick Guide to Boat Storage.)
At the very least, flushing your inboard engine is a step that forces you to inspect the inputs to your engine – where plants, debris, or critters can lodge themselves.
What Is An Inboard Water-Cooled Engine?
Unlike outboard engines, your inboard boat engine uses the water to cool itself. (It’s a little like the old air-cooled cars that were replaced by internal cooling systems starting in the 1970s.)
An inboard water-cooling system works very efficiently…in water. But if the water intakes are only sucking in air – i.e., you try to test your inboard without following the steps outlined here – you can overheat and destroy your engine very quickly.
You should never try to dry-start your inboard boat engine.
How Do I “Fake A Lake”?
While your engine is a remarkable piece of technology, the process of land-starting your boat and running your engine while still on the trailer is about as low-tech as it gets.
Basically, you’ll use a mechanical component to surround your engine’s intakes with water – this is the “fake-a-lake” engine flusher. This device is technically called a Circular Cup Muff Plunger with Hose Fitting. (But don’t let the long name fool you: it’s essentially a glorified toilet plunger with a kickstand!)
Once you have a fake-a-lake device in hand, the most important part of this process (by far) is monitoring your engine temperature for possible overheating. Note that you’ll need to monitor for overheating the entire time you’re flushing your inboard engine.
Other than that, your primary concern should be ensuring there’s adequate water flowing and no signs of water leaks.
What Other Equipment Do I Need?
A basic garden hose will act as the “lake.” Just be sure that you have adequate water pressure, and be vigilant for kinks, as an interruption to the cooling water can lead to an overheated engine
The other key piece of equipment is the temperature gauge on your boat. Typically, you want to keep the engine running in the 160-170 degrees Fahrenheit range.
Finally, though not a piece of “equipment” per se, you’ll want to consult your owner’s manual to read any specific guidelines for engine flushing. (For example, double-check the correct temperature range for this procedure, which may vary by make, model, and engine options).
What Are the Parts of a Fake-A-Lake Device?
The classic fake-a-lake tool has three key parts:
- The plunger cup: The part that is applied to the bottom of the boat to cover the impeller intake valve (the water intake hole that is used to suck water in)
- The water flusher leg: The part that looks like the handle on a toilet plunger. This is like a kickstand that keeps the plunger cup pressed against the bottom of your boat.
- The hose valve: The part where you attach your garden hose to the water flusher
A Step-by-Step Guide to Using the Water Flusher
Step 1: Connect the Garden Hose
Connect the garden hose to the flusher’s plunger piece before attaching it to your boat. Turn on the water to check for water pressure. (We’re not using a water pump here, so you’ll need good, steady water pressure.) Then turn off the water hose.
Step 2: Locate the Impeller Intake Valve
Get under your boat and find the impeller intake valve (the water intake for the inboard engine). You’ll want to sit the plunger cup as squarely as possible.
Step 3: Place the Plunger
Adjust the plunger leg to push the plunger upward and firmly in place.
Step 4: Turn on the Water Again
Once the plunger cup fills, you should see water escaping over the edges of the plunger cup.
Step 5: Run the engine
Look to confirm that less water is escaping from the plunger cup. This ensures that water is being sucked into the engine.
Step 6: Monitor Your Boat Egine’s Temperature and Your Boat’s Exhaust
Check your engine temperature constantly. You’ll also want to monitor your boat’s exhaust to ensure your boat’s engine is flushing out water properly. When flushing, be sure to take note of any substance or foreign object that comes out of the exhaust. If there is debris, your boat’s water intake may be compromised and need replacing.
Final steps
Lastly, turn off your engine. Turn off the water hose, and remove the water flusher.
Running the Engine Properly During Water Flushing
When flushing an inboard engine, your ultimate goal should be to avoid overheating your engine. This means checking your temperature gauge and ensuring a consistent water supply.
In addition to keeping your eye on the temperature, you’ll want to resist the urge to rev the engine. While it may feel like you’re fast-tracking the process of expelling any debris out of the engine, it also increases the rate that the engine is sucking up water. Inadvertently, you may increase the possibility of your engine sucking up more water than is being replenished in the plunger.
Troubleshooting Common Issues
Insufficient Water Pressure
Should you encounter insufficient water pressure while starting your inboard boat engine out of the water, begin by inspecting the water source for any issues impacting water pressure. Check the hose connections for leaks or loose fittings that may be causing a drop in water pressure.
If the water pressure remains low after addressing these issues, consider seeking professional assistance. DIY maintenance is great (see our Complete Guide to Boat Maintenance), but not at the expense of potentially destroying your engine.
Water Leakage
Water leakage can occur if the fake-a-lake device is not properly attached to the engine’s water intake. To fix this issue, follow these steps:
- Inspect the device for a secure fit.
- Tighten any loose connections.
- If water leakage persists, consider replacing the device or seeking professional assistance.
In addition to checking the device’s fit, inspect the garden hose and connections for any signs of damage or wear that may be causing water leakage. Replace any damaged hose and ensure all connections are secure to prevent further issues.
Engine Overheating
If your engine overheats while starting the engine out of water, immediately shut off the engine and investigate the cause.
Potential causes of overheating may include blockages in the water flow, clogs in the raw water strainer, or a damaged impeller. It’s critical that you fix any of these problems before running the engine again.
Finding Storage that Protects Your Inboard Engine
To prevent debris from collecting in the inboard engine, you might think of blocking your inboard engine’s water intake, which is a good way to destroy your engine.
Many boat owners fail to realize that proper storage is one of the best ways to keep dust, debris, plants, and critters from blocking the intake valve.
The best option is enclosed, covered parking – such as in your garage. You can also find affordable and easy indoor boat storage options online by searching the many boat storage options nearby on Neighbor.com, a peer-to-peer storage marketplace.
