While repairing your outboard engine, you may need to conduct several tests to verify whether the outboard is functioning as required. You obviously can’t take it all the time for these tests, and that’s where flush muffs or muffs come into play. So how long can you run a boat on muffs?
Whether charging your battery or keeping the fridge running at anchor, keeping your muffs running for about five to seven minutes would be best. You want the outboard engine to warm up enough but not overheat – so ensure you’ve got a solid cold water supply.
Different engines have different requirements. Whether you have a four-stroke outboard or a two-stroke outboard, it would be in your best interest to follow the manufacturers’ instructions about maintenance. Let me guide you on what you need to know about flush muffs. 
What Are Boat Muffs?
Some of you newer boaters may not have heard of boat motor muffs. These are special tools used for outboard motors. When the motor runs, it doesn’t have a radiator to cool it like a car engine. Instead, there are small water inlets down the engine shaft near the propeller.
The engine draws up water as the boat travels along, circulates the water in the engine to cool it, and spits the water back out, usually facing backward. You may have seen that trickle of water squirting out of the outboard and wondered what it was – well, that’s it.
Now, muffs look very similar to earmuffs to keep your ears warm – hence the name. Boat motor muffs have two cups that clamp over the motor shaft, covering the water inlets. There is a central hose fitting on the muffs, so you can attach your cold water garden hose.
This way, you can run your outboard while your boat’s on its trailer without fear of overheating the motor and damaging it. That is, as long as you have a good supply of cold water moving through your hose and muffs to cool the motor.
How Long Can You Run A Boat On Muffs?
Flush muffs, or ‘muffs’ for short, are reasonably cheap boat accessories that you can find at your local boating store. Muffs are the way to flush an outboard motor and keep it from burning up. All you have to do is attach to a garden hose, place muffs over the motor’s water intake, turn on the water, start the outboard engine and let it do its thing.
It’s best to run your motor while on muffs for 5 to 7 minutes. Muffs may seem trivial, but boat owners who don’t have their vessel in the water 365 days a year are a godsend.
Maintaining and repairing your boat is one of every boat owner’s chores to attend to every year, especially if they’re constantly using the boat. Unfortunately, mother nature is not kind, and your boat will start to wear out without the necessary maintenance.
A muff is one of the tools that allow you to maintain your outboard’s engine without it being in the water and without you burning out your water pump.
Fortunately, we’ve curated some maintenance tests you can conduct with the muffs down below. Be sure to check them out.
Is It Bad To Run An Outboard On Muffs?
No, it is not harmful to run an outboard engine on muffs. Muffs allow you to conduct maintenance tests on your outboard engine. Without muffs, you would fry your water pump. At that point, you would have to repair it yourself (if you have an engineering background), or you might have to consult a marine engineer to fix it for you.
Many boat owners with outboards will highly recommend getting muffs. They are cheap, but they allow you to run your outboard without submerging it in the water. Not all boat owners have the capacity to keep their boats in water year-round.
Furthermore, there’s the issue of winter. Even if your boat is submerged, you need to warm up the engine. It’s the best way to avoid permanent damage that will affect its performance moving forward.
Some boat owners do not like using muffs. Instead, they will submerge the outboard parts in a large bucket or a makeshift tub and conduct the tests. This method is especially beneficial when testing outboard water pumps.
The Importance Of The Muffs
Here are a couple of reasons you should have a muff and what makes it an essential and handy tool for any boat owner.
- It allows you to conduct maintenance and repair tests on your outboard engine.
- It reduces the risk of burning out your water pump.
- It reduces unnecessary maintenance costs, such as going to a marine mechanic.
- Muffs are incredibly cheap. You can find one at your local hardware for around $7.
Muffs are a must-have accessory for any boat owner. Not only that, but once you buy a muff, it no longer becomes an accessory but more of a complementary item to your boat. (source)
How To Maintain An Outboard Engine
Maintaining your outboard engine varies according to the engine you have. Some of the maintenance points mentioned are from a general standpoint. It would be in your best interest to check the manufacturer’s instructions on maintaining the outboard engine.
If it didn’t come with instructions, you could check the manufacturer’s website for more information. Let’s get started on maintaining your outboard engine.
Maintaining Timelines And Schedule
Your maintenance schedule depends on how often you use your boat. The more often you use your boat, the more tests you will have to conduct. Here are some of the tests you will have to conduct to maintain the state of your boat: 
- Oil pressure checks
- Exhaust checks (unless your engine has a dry exhaust)
- Transmission oil level checks
- Pulley belt tension checks
- Air filter checks and replacements
- Header tank checks
- Fuel tank checks
- Cooling system checks
- Coolant hoses checks
- Hose clamps checks
There are a lot of repairs and replacements to make that boat owners have to take into account. Furthermore, different engines have different needs. Outboards are just one example of engines present in the marine industry. (source)
For example, four-stroke outboards and two-stroke outboards have different ways of checking and changing the oil. The same applies to the transmission fluid.
You also have cleaning, painting, and waxing maintenance methods, but those don’t apply to the outboard engine. All in all, maintaining your boat can come across as complex, but once you get the hang of it, it’s pretty straightforward.
How Long Does It Take A Boat To Overheat?
According to Boat US Insurance, engine fires caused 15% of fires on recreational boats between 2015 and 2019. The engine compartment is the primary source of fire for the rest of the different types of fires. (source)
A boat engine can overheat in a matter of minutes. It takes less than five minutes for a boat to warm up, and any longer increases the temperatures in the boat engine greatly. It’s similar to a car.
Are Muffs A Worthy Investment?
In our opinion, muffs are worth the investment; not only that, but they are a budget-friendly investment that allows you to test your outboard when it’s out of the water. They also reduce the risk of engine fires. They may not be everyone’s cup of tea. Still, they do their job efficiently and offer other significant benefits to boat owners.
Should you buy muffs? Absolutely. Will you regret it? Unlikely. The majority of boat owners will recommend buying muffs for your outboard. They offer more good than bad.
- Nigel Calder, Boatowner’s mechanical and electrical manual (New York: Bloomsbury Publishing PLC, 2017) 832.
- Randy Vance, Power Boating for Dummies (New Jersey: Wiley Publishing Inc, 2009) 384.
- John Tiger, Outboard Flushing, The Right Way, Boat US Magazine, May 2014, Accessed March 18, 2022.
- Boater Exam, Boat Engine Types Explained, Boater Exam, Accessed March 18, 2022.
- Boat US Insurance, Analyzing Onboard Fire Claims, Boat US Insurance, February 2021, Accessed March 18, 2022.