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wakeboarder3780

Running Your Boat With No Impeller And No Water Intake

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wakeboarder3780

Just want to confirm something. If I were to remove my impeller I could safely run my boat with no water intake until the boat reached 160 for an oil change correct? If you think you can't please state why.

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Indyxc

How will you know when the engine reaches 160? No fluid circulating means no water on the temperature sensor. Not a good idea for many more reasons. Run it on a fake a lake

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haycutter

Why would you want to go through that? What are you trying to save? Help us understand.

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wakeboarder3780

It's for a boat where a buddy had his winterized by a dealer. They handed him the impeller and it's removed already. I was going to have them install the new one after doing the oil change so they'd have no way of burning up their impeller on a lack of water flow. They stated their garden hose pressure is VERY low and I'm concerned about burning up their impeller. I understand it was a goofy question but now you understand.

Indyxc, I wasn't aware the temp sensor was based off of water flow? That doesn't really make sense to me. On the other hand I wasn't exactly going to use 160 as a hard and fast. I was probably going to run it for a minute or so or until the block felt warm. I'm not a firm believer in NEEDING to run the engine prior to an oil change.

That being said I don't believe the temp gauge is solely based of of water flow, here's why. I overheated my engine on my 89 sunsetter because I ran it in the driveway with poor waterflow (which unknowing to me torched my impeller that day). I then took it out on the lake idling around and it overheated on me. My temp gauge was pinned (and there was no water flow). There seems to be more to it than you're suggesting that no water flow means no temp reading. I think it just means less accurate readings and if anything, the readings would be lower than actual. Would you agree?

What are your other reasons this is bad for?

Edit: This is less about "what I'm trying to save" and more for me to make sure I understand how things are working in boats.

Edited by wakeboarder3780

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Malibuzer

Indyxc, I wasn't aware the temp sensor was based off of water flow? That doesn't really make sense to me. On the other hand I wasn't exactly going to use 160 as a hard and fast. I was probably going to run it for a minute or so or until the block felt warm. I'm not a firm believer in NEEDING to run the engine prior to an oil change.

I don't think that is what he meant. What the water does is transfer the heat to the sensor much faster than the air does. It would have to get the metal really hot to transfer the heat into the temp probe. Does this make sense?

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Bill_AirJunky

Just want to confirm something. If I were to remove my impeller I could safely run my boat with no water intake until the boat reached 160 for an oil change correct? If you think you can't please state why.

No way I'd do it that long. I start mine for a second or two all the time. But a minute.... I don't know what would happen. :crazy:

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wakeboarder3780

I don't think that is what he meant. What the water does is transfer the heat to the sensor much faster than the air does. It would have to get the metal really hot to transfer the heat into the temp probe. Does this make sense?

Yes that makes sense to me which is why you couldn't necessarily trust the temp gauge, it would give you a lower temp than actual. That does make sense to me.

Do you have any idea of what else would be a concern? For my current knowledge I can't think of anything else that would be "bad" and I honestly would only fire it up for a minute or so anyway.

I mean the way I see it, when you fire up your boat, the t-stat is closed until the engine heats up anyway. That means all the water you're pumping through, goes right out the backside without ever going through your engine. When the t-stat is closed, the only other thing water is doing is going through the tranny cooler, but the boat isn't in gear and the transmission shouldn't generate any heat.

If someone can tell me how this would harm a boat, please let me know. I know this would make many people uneasy, but that's not what I'm asking. I'm asking what specifically the harm is so I can learn something I don't know (or for someone to confirm with me that there is no real harm as long as I don't allow the engine to overheat).

Edit: changed verbiage to be more clear

Edited by wakeboarder3780

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Bill_AirJunky

I know you will melt the exhaust hoses for sure. I suspect there will be other hoses that get torched too.

Also, if your engine has aluminum heads on it, they will warp super easily & it will blow a head gasket. I don't know if it would be inside of 1 minute or not. Could be an expensive lesson to learn.

Something else that will go early is the rings. Excessive heat will warp them & cause them to leak, cylinder compression will drop, it'll begin burning oil. Again, I don't know if it will be inside of 1 minute or not but wouldn't risk it either.

Edited by Bill_AirJunky

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martinarcher

Without the impeller installed and a external water source you basically have a fancy, very expensive way to boil water in a hurry. If you start a boat without and impeller, the blocks water pump will circulate the small amount of water in the block. This water pump is the same as what you have on a GM 350 automotive application. It is meant to circulate water to the radiator (heat exchanger), which will return cool water back into the block and allow the internals to stay cool.

On a boat, most do not have a radiator therefore we depend on fresh cool incoming water from the impeller to keep our engines cool. If this is missing and we are only recycling the small amount of throughout the block. Of course the water will heat up very quickly, but the danger is the cylinder walls and heads will heat up faster that you can safely monitor. By the time your hand detects the block is "hot", the metal closer to the fire will be much too hot. The gauge on the dash also will vary depending on where it is on the block. I know my temp sensor is pretty high on the block and I would be skeptical in this case if it would truly be impressed by a good flow of water. If not, it will give a false, lower temp reading than the block as mentioned above.

Is it safe to run the engine for 60 seconds with no impeller...sure I don't see why not, but I see lots of reasons why I would run it with the impeller and fresh water coming into the engine. If you want to take a short cut to change the oil before the re-install the new impeller, I would take two and change it cold.

If it were me, I would rather do it right and install the new impeller, find a good source of water and bring the boat up to temp properly, then change the oil. I would assume you would want to test run the boat with the new impeller before taking it to the lake as well. I know my boat has never seen lake water in the spring without a driveway test run first. I do everything I can to try to avoid being "that guy" at the launch in the spring. Biggrin.gif

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Lance B. Johnson

Everything that Bill listed is at risk.

The oil should have been changed when it was winterized.

If it were my boat I would reinstall the impeller and do it right.

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jkendallmsce

Just want to confirm something. If I were to remove my impeller I could safely run my boat with no water intake until the boat reached 160 for an oil change correct? If you think you can't please state why.

So what do you expect to gain by running the engine for any amount of time, vs changing the engine oil as it is now (cold)?? The only difference is that it will take longer to drain the oil cold.

The last time the engine was run (assuming it was up to or at operating temp), the oil was being pumped thru the engine and oil filter. Then it was shut off and cooled and the oil drained to the lowest point, or the oil pan (where the drain hose is).

The only advantage to changing the oil while warm, is that the engine components are freshly coated with oil.

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CedarLakeSkier

Without the impeller installed and a external water source you basically have a fancy, very expensive way to boil water in a hurry. If you start a boat without and impeller, the blocks water pump will circulate the small amount of water in the block. This water pump is the same as what you have on a GM 350 automotive application. It is meant to circulate water to the radiator (heat exchanger), which will return cool water back into the block and allow the internals to stay cool.

This is true, but if the boat was winterized, are you sure there is any water in the block to circulate? If not, it will heat up very quickly and as previously mentioned, the temperature gage will most not likely register it as quickly as it should since there is not liquid to measure the temperature of. I would be VERY uncomforatable doing this for a minute. Even if I can't point to a specific thing that would fail, I simply would not want to take the chance.

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martinarcher

Exactly. Everything I mentioned above assumes you left the block full of antifreeze over the winter and it is still full.

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vette-ski

My short answer: I would do it if I felt I really had to (although I'm not sure I followed the rationale of why you wanted to do this)

My caviat: I know I am responsible for my actions and have to fix anything on the motor I mess up. But I have the knowledge and tools to do that. I wouldn't come back to the board complaining that I blew up my engine. I would just fix it and call it a lesson learned for the next time I want to experiment.

Of all the things posted above, the only thing I'd worry about is roasting the exhaust hoses. But the guy that posted the other day about thinking he seized his engine after an overheat and running 5 min with no water never mentioned a word about melted exhaust hoses, so I suspect they are fairly tolerant of heat. But I don't know this personally. I, myself, wouldn't worry about the engine for a minute or less. Everyone on this board runs their boat for a minute with no water flow through the motor every day they hit the lake, they just may not realize it. About the temp sensor, it may not be as accurate if the intake is dry, but it's just a chunk of brass hanging into the water jacket. It's not isolated from the intake manifold. When the intake heats up, so will the sensor.

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wakeboarder3780

Thanks for the input guys. Please keep in mind the main point of this discussion was a theoretical discussion for me learning some more.

I understand the points listed by Bill and Martin and I thank you for them, those are along the lines of what I was looking for.

The main problem I have to deal with when helping these other guys is they get certain things in their head without really knowing why they're doing what they're doing - for instance they definitely want to run the boat prior to changing oil. If it were my boat I'd drain it cold and I wouldn't lose an ounce of sleep over it.

The main thing I was trying to save them was a possible torched impeller. My official advice going forward is going to be they drain it cold, OR install the original impeller back in to warm it up with, drain oil, then replace with a brand new one (they should anyway because this is the first year with their new-to-them boat).

I did learn some things from this thread and I thank everyone that chimed in. Wish I knew how long it actually took for things to get warm inside just for funsies :)

Edited by wakeboarder3780

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wakeboarder3780

My short answer: I would do it if I felt I really had to (although I'm not sure I followed the rationale of why you wanted to do this)

My caviat: I know I am responsible for my actions and have to fix anything on the motor I mess up. But I have the knowledge and tools to do that. I wouldn't come back to the board complaining that I blew up my engine. I would just fix it and call it a lesson learned for the next time I want to experiment.

Of all the things posted above, the only thing I'd worry about is roasting the exhaust hoses. But the guy that posted the other day about thinking he seized his engine after an overheat and running 5 min with no water never mentioned a word about melted exhaust hoses, so I suspect they are fairly tolerant of heat. But I don't know this personally. I, myself, wouldn't worry about the engine for a minute or less. Everyone on this board runs their boat for a minute with no water flow through the motor every day they hit the lake, they just may not realize it. About the temp sensor, it may not be as accurate if the intake is dry, but it's just a chunk of brass hanging into the water jacket. It's not isolated from the intake manifold. When the intake heats up, so will the sensor.

I would also say when I legitimately overheated my 89 sunsetter, the hoses were fine afterwards. They are extremely tough and durable. I even took them off and checked for soft spots. They can take a beating.

On your second bolded section, those were my thoughts exactly because I do a short winterize where i drain the block every night in early spring and late fall so the block has no water in it when i fire it up. Equivalent scenario to buddies boat currently.

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Bill_AirJunky

I'd use something like a mity vac to suck the oil out. Set it up & walk away. Have a beer. In an hour, 99% of the oil will be drained. Running the engine to heat up the oil is only going to make it a shorter time to drain... no other benefit. If they insist, and installing the impeller & a water source isn't an option, maybe try a magnetic oil heater?

MIT7400.jpg31pa6JwYokL._SL500_AA280_.jpg

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wakeboarder3780

Thanks bill, I'm guessing if left with those options they'd probably let it go because they seem to focused mainly on saving money :) Thanks for the responses :yahoo:

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Deephaven

Not sure how happy your water pump will be running dry. I wouldn't do it....but I also wouldn't worry about changing cold oil. Just let it drain longer and you are golden.

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jk13

Not sure how happy your water pump will be running dry. I wouldn't do it....but I also wouldn't worry about changing cold oil. Just let it drain longer and you are golden.

And make sure you have a large enough catch container if you walk away or let it drain overnight.

Sucks waking up to find your container overflowed, even with a plastic tray under it just in case. Just sayin'. :whistle:

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Lance B. Johnson

Thanks bill, I'm guessing if left with those options they'd probably let it go because they seem to focused mainly on saving money :) Thanks for the responses :yahoo:

Tell them to save money by not running the engine without water circulation then. :)

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electricjohn

It will take longer than 10 minutes of running time @ idle speed to heat the oil up. The oil had all winter to drip down to the pan, so just change it as is and give it an extended drain time (like overnight).

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SunriseH2OSkier

It will take longer than 10 minutes of running time @ idle speed to heat the oil up. The oil had all winter to drip down to the pan, so just change it as is and give it an extended drain time (like overnight).

+1,000,000

Running the engine for 60 seconds will do nothing to warm the oil. It will be every bit as thick as it was before starting the engine. The only thing that will be different is that less of the oil will be in the pan.

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Bill_AirJunky

Tell them to save money by not running the engine without water circulation then. :)

Funny how the obvious is soooooo true. :rockon:

BTW, I've tried just opening the engine drain & letting it go. Depending on how cool it is all night, and how thick the oil is, it may or may not drain at all. The MityVac is great for sucking that thick oil out. I don't even own one... i just borrow my buddies'! Hows that for cheap.

I don't see how putting the impeller in the engine & running the garden hose to it costs any money for the user..... are you charging them? By time?

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Sixball

Running a engine dry can be done but your water temp gauge is not even close to accurate dry. The engine will have hot spots. We ran engines without water circulating in drag racing. We ether filed them with water and caped them off or filed the water jackets with other things epoxy. Now days they just don't put water jackets in the blocks and heads they are billet.

The reason to change oil well hot or warm, the sediment is suspended in the oil and comes out with the oil. when you leave it for long time it settles and clings to the pan.

Out some old used oil in a jar and leave it. Then dump it out and see what you have left.

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