Why I NEVER Flush My Outboard!

And just for a point of reference, you wouldn't be able to tell the difference between any of these impellers. All that's eating away, all that's eating away, and then all this is pretty much gone with a hole there. Earmuffs on the water pickups like this. All right. Now we're looking pretty good. There are two sides to the flushing coin. Whether to flush or not to flush. And a few main arguments about flushing, like getting the thermostats to open up to flush the dump side, and whether or not you can run the engine on the flush attachment or not. We've also got basically three separate ways to flush an engine. The first is to use the flush attachments that are on the engine. The second is to put a set of earmuffs on the water pickups like this. And the third is to submerge the entire lower in a bucket like say a trash can or a drum full of water. Let's start this conversation with running the engine on the flush attachment first though. I'm, not sure why but a lot of people like to blanket every single engine and say that you cannot run the engine on the flush attachment. With the main reasoning behind this being that you will either burn up the impeller or overheat the engine. Now with a couple of disclaimers. Number one, this all depends on the water pressure of the hose that you're using. If you have normal water pressure which is somewhere around 40 psi, then you'll be good to go with what we're talking about here today. If you have sprinklers running, a dishwasher, your washing machine, and you are filling up a pool leaving you with like 10 psi of water pressure, then that is not enough water for this discussion. The same theory goes with having multiple engines on the back of your boat and running a hose splitter to flush them all at the same time. You are cutting your volume and pressure down tremendously. So a little thought and maybe some common sense will need to be applied there. Also, say you have a larger engine like a v12 600 horsepower or even a 425 V8 from Yamaha, you aren't going to have enough volume of water to cool the engine during this process. So you just need to keep those things in mind. But for pretty much any other size engine, especially smaller ones, we'll be good to go. And finally, the speed of the engine is also going to be a major factor here as well. And with all of that being said, the real answer is yes, you can run your engine on the flush attachment without burning up your impeller. As long as you keep the engine at idle, you will be fine. The water will make its way down to the impeller to keep it cool and keep it from burning up. But you never want to rev the engine up while it's on the flush attachment. The real question here is what exactly are you wanting to do? If you are just trying to do some diagnostics or check something out on the engine, then hooking up the flush and starting the engine to leave at idle for say one to two minutes, that's perfectly fine with no issues. Hundreds of thousands of people do that all over the world. But if you rev the engine up while on the flush attachment, the impeller is going to push the water up off of it, letting it run dry and eventually burn itself up, which is why you never want to rev it up while on the flush attachment. Just for a demonstration here, we've got an engine that's got an impeller with about 200 to 250 hours on it. What I'm doing here is I'm going to put this on our hose here on the flush attachment and we're going to run this engine for like 10 to 15 minutes. We'll just let it sit here in idle and then we'll pull the lower unit and check the impeller to see if it's burned up. And I'm going to start the engine. We're going to watch the time on the clock and the engine with the flushing and we're going to let this thing run for like 10-15 minutes to see what happens. All right, engine's running. We've got the flush. We've got it onto the hose. We're peeing out there. Normal hose pressure. We've got our watch. We've got our camera. So we'll let this thing run and then we will pull the lower unit and check the impeller to see if truly you will burn up your impeller by running your engine on the flush attachment. Well, here we are. We have been 15 minutes on the clock. You can even check the camera here, too. You got 16 minutes actually. So that thing's been running for 16 minutes. Let's go ahead and check our temperature here. Let's see here. We're at 143 degrees. So temperature's right. Everything's running. Thermostat's opening up at 143 on these engines. So that's right where it should be. We're not running hot. Not messed up at all. And so now after 15 minutes, I mean, I guess we can go a little bit longer, but there's not really any point. You can run this thing for another 30 minutes if you wanted to. But what we need to do now is we're going to kill the engine, pull the lower unit, and we will check what the impeller looks like to see if it's true that you're going to burn up your impeller when you run your engine on the flush attachment. So let's see if this is true. Also one other thing just to show you that with it on the flush attachment, just on the flush attachment, you got water coming out from in here. You got water from here. You got water from the prop. But if you look, you've also got water coming out the water intakes. So we have water pouring out from the water pump impeller housing. I mean, that's plenty of water to cool that impeller. Again, this is on an L6. It's not on a V6, like a big V6 or a big V8 or anything like that, but the concept's pretty much the same. So let's check this impeller out and see what it looks like. Well, it just looks like an old impeller. Kind of rolled over a little bit. Normal wear on the back. Normal wear on the front. Again, this is probably 200 hours, 250 hours on this impeller as it is. But it looks no different than this impeller here or this one here or any of the other hundreds of these that you take out. You can see that it is evenly wearing all the way around. But there's nothing catastrophically wrong with this impeller. You could have run another 100 hours on it. And just for a point of reference, you wouldn't be able to tell the difference between any of these impellers. So these are all used impellers and they all wear the exact same way where from this little rib here that runs down here. That's all they all wear off like that. This one's been sitting in a housing too long, but they all wear in the same manner and if you were to look at these you won't be able to tell which one was the one that was ran on the hose and which one is just a used impeller. This one's actually a fairly new impeller. So that's why that one sticks out straight and doesn't have any bends to it. Except for a slight bend that's been used just barely. Whereas the rest of these you can see pretty nice bend. So of all these which one do you think is the one that got ran on the flush attachment? Probably think this one or probably this one. Maybe this one. But it's actually this one. So as you can see no problems here. Now if you need to raise the RPM then you need to put it on the set of muffs and depending on the brand and model of the engine you have you might also need the covers for the lower water pickups right here. Another side note here while i'm thinking about it. If you are using your flush attachment or the muffs you really want to limit the engine run time anyway. It's just better for the impeller and the engine period. If you need to run it for more than 15 minutes then I would go with the third option of putting it into a bucket or even a test tank. Or just take the boat to the water and stick it in the water. Honestly when you think about it we are talking about a rubber impeller that has a shelf life based on age temperature and run time. If you need to run the engine for more than 15 minutes you might just want to put it back in the water to get some back pressure on the engine anyway. Not to mention having the proper volume of water to run through the engine to cool the engine and the impeller as well. With that subject covered though let's move on to talking about what we're actually doing when we flush an engine. As well as who should be flushing their engine and who doesn't. Most of the cold freshwater boaters probably never flush their engines. Unless they're running in some dirty brackish water or water with a lot of algae or shallow water with a lot of grass that they can pick up. Or if they're beaching the boat in a cove where they can get out and get in the sand. They really don't need to. I mean freshwater flushing a boat that mainly runs in freshwater. What's the point? Many lake boaters are still running engines that are 20, 30 or even 40 years old that have never been flushed a day in their life. So that's pretty simple. Then you got people like charter captains that pretty much run the boat every single day. There are tons of charter and commercial boaters that never flush their engine ever just because they run it every single day. So again, what's the point? Not to mention that some charter boats and commercial boats will wear out an engine in less than eight years anyway. But recreational boaters that are near the equator in warm saltwater, this is where the problem starts to arise. Because the engines tend to sit and when we talk about what we're trying to accomplish with the flushing, we need to take into account what is happening. An engine temperature is normally at around 140 to 150 degrees depending on the engine. Like on an L6 Verado, the thermostats on this engine tend to open up at 143 degrees. So it usually runs pretty close to that temperature. Then when we turn the engine off, the temperature is going to stay up there for a little while since it no longer has the cooling water flowing. As the water evaporates over time and probably fairly quicker than you might think, remembering the engine temperature as well as the outside air temp of wherever location you are located at, the water is going to evaporate pretty quickly leaving any dirt, salt, calcium, or other mineral deposits behind. So the effectiveness of flushing the engine is to do it fairly quickly after shutting off the engine. This way the water has less time to evaporate leaving the deposits behind. And the fresh water will flush out all of the saltwater or minerally rich brackish water out of the system, cooling the metal engine down and leaving minimal deposits behind. Now if you leave the engine for say 12 hours or even overnight, if you think about it, when you flush it, you really aren't doing that much. Because the time has already passed enough for the water to evaporate and leave the deposits that corrode and put out the metal parts of the engine. Mind you, it usually takes years for the salt to build up based on the amount of use the engine sees as well as the location where it is kept. So the damaging effects of the deposits might take 10 to 15 years to show up. At which point it's beyond a financially wise decision to repair if you have to pay someone to fix it. Usually because of the parts that corrode out first being the exhaust manifolds where the water evaporates the quickest, leaving the most deposits that eat out the metal the soonest, which is locating at a mating location right against the powerhead or the block of the engine. Meaning that the exhaust manifold and the engine block is corroding out basically destroying the engine. For the cost of the powerhead, the exhaust components, and the labor to change, it's a big reason why some engines get sent off to the dump. There are also a lot of products like Salt-A-Way that you can run through the engine while flushing that will help tremendously. But we've got a video about these that you can check out here. Now if you're wanting to get the most out of your engine and keep it for a long long time, and you are located in an area where the water that you boat in lines up with these conditions, then you should be flushing the engine when you get done using it. Especially if you're using it moderately throughout the year. Unfortunately, when you think about it, that even means when you're going to use it again the next day. Though I'll admit, I usually don't even do that myself. Just because I think you can combat the buildup by running the Salt-A-Way through the engine, say every three months or so, it keeps it clean and lets you be lazy in the flushing department. Now with the understanding of flushing, let's talk about the running the engine when flushing versus the not running the engine when flushing. With the same concept of running the engine while on the flush attachment, the water is getting down to the impeller to flush out the water pump housing and the water pump impeller, as well as the exhaust and virtually all the other cooling passages that are in the engine. Honestly, engine manufacturers and engineers put these flushing attachments where they put them for a reason. But that's why there are three different ways to flush the engine, like what we talked about earlier. Because there is the other side of the coin where the cooling water won't be getting to the other side of the thermostat, since the thermostat will be closed. Now, if you keep the boat in the water, you can't run the engine when flushing it anyway, because you've got the engine trimmed all the way out of the water, so you really don't have a choice. And depending on the model of the engine, the amount of stuff that gets flushed will vary. Like on the L6, here's the thermostat up here, and here's a hose that dumps the water down to here. So pretty much all this isn't getting flushed from the attachment on this model, which can lead to the buildup that you can see here at this location, where when we take this V8, the thermostat is up here on the top of the exhaust manifold and dumps directly into the exhaust. So the cooling water is actually getting to both sides of the thermostat, theoretically in this case. Obviously the best and most efficient way to flush an engine is to stick it in a bucket and run it in fresh water. You can even hook up a hose to the flush attachment and run the salt away through the flush as it runs in the bucket. And that would probably be the most effective way to flush an engine if you want. Now, there is also the case where you might have ran the engine on ground, packed it full of sand, and now you've actually got to take stuff apart to get all the dirt out. But that's an extreme case, and flushing isn't going to help you there. But hopefully at least you understand a lot more now about flushing than you did before.