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Old 26-11-2020, 07:18   #1
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Can you run a Marine Diesel without Water ?

Hey Guys

Quick question regarding marine diesel engines. I've heard lots of "lore" regarding this issue and am interested in sifting through the opinions and getting to the facts.

Now that engine winterizing seasons has come and gone, many techniques of winterizing has been completed.

Can you run a marine diesel on the hard, with no water for less than 5 minutes?

Key point, less than 5 minutes.

Why would you do this?

1. Expel anti freeze prior to launch to safely dispose of, instead of dumping into the water

2. Check for fuel airlock prior to launch, to avoid a tow and additional fees associated with delaying on a crane

3. Winterizing with no constant water source, but plenty of anti freeze

4. Maintenance in remote location, no constant water source

With this in mind, we know engines are able to survive a blown out fresh water impellor (which essentially provides water to the engine the same as a hose would). Plenty of youtube sailors have documented this. In some cases the smoke filled the boat and engine room.



Thoughts?
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Old 26-11-2020, 07:27   #2
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Re: Can you run a Marine Diesel without Water ?

Without water, you will melt your water pump impeller. Otherwise, no problem for short runs, just don't let it overheat. It's common to let the engine suck from a 5gal bucket of water for short runs on the hard.
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Old 26-11-2020, 07:37   #3
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Re: Can you run a Marine Diesel without Water ?

Running an engine without circulating coolant isn't good for it. A block full of coolant will slow the heat buildup but it won't stop it and the parts in the center of the heat buildup will be affected the most. Piston rings, valve guides and seats are all dependent on cooling to avoid overheating and failure. It can be done, but you can't prolong the run time.

In my opinion, if you absolutely must do it then...

For the Anti-Freeze: Use the same method you used to get the AF into the engine and pour fresh water into the cooling system while catching the AF in a bucket as it comes out. Filter the AF into the original jugs (coffee filters in a big funnel) and store for reuse next winter.

You can fill a big bucket with fresh water and have someone pour it into the system as you run the engine for the fuel system checks. If it's fresh water and there's nothing else in the system, you can let it pour out onto the ground instead of catching it. Of course that makes a mess and you have to go refill the pouring bucket when it's empty instead of just swapping buckets, but...

Most launching spots have a dock to tie up to verify there aren't any leaks right after launching. You ought to be able to do pre-season engine checks there and not tie up the slings while also avoiding a tow back for haul out and repairs. Although I have no idea what repairs would need to be done on the engine that can't be done while the boat is on her own keel.
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Old 26-11-2020, 07:55   #4
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Re: Can you run a Marine Diesel without Water ?

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Originally Posted by jt11791 View Post
Without water, you will melt your water pump impeller. Otherwise, no problem for short runs, just don't let it overheat. It's common to let the engine suck from a 5gal bucket of water for short runs on the hard.
I agree with you.

In my case, a bucket of water would work if I could get my hoses off. This year because of covid power was shut down

I need a heat gun to disconnect hoses.

Do you know how long an impellor can last before it would melt? or its RPMs?
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Old 26-11-2020, 08:00   #5
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Re: Can you run a Marine Diesel without Water ?

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Originally Posted by Rob_P View Post
Running an engine without circulating coolant isn't good for it. A block full of coolant will slow the heat buildup but it won't stop it and the parts in the center of the heat buildup will be affected the most. Piston rings, valve guides and seats are all dependent on cooling to avoid overheating and failure. It can be done, but you can't prolong the run time.

In my opinion, if you absolutely must do it then...

For the Anti-Freeze: Use the same method you used to get the AF into the engine and pour fresh water into the cooling system while catching the AF in a bucket as it comes out. Filter the AF into the original jugs (coffee filters in a big funnel) and store for reuse next winter.

You can fill a big bucket with fresh water and have someone pour it into the system as you run the engine for the fuel system checks. If it's fresh water and there's nothing else in the system, you can let it pour out onto the ground instead of catching it. Of course that makes a mess and you have to go refill the pouring bucket when it's empty instead of just swapping buckets, but...

Most launching spots have a dock to tie up to verify there aren't any leaks right after launching. You ought to be able to do pre-season engine checks there and not tie up the slings while also avoiding a tow back for haul out and repairs. Although I have no idea what repairs would need to be done on the engine that can't be done while the boat is on her own keel.
I'm talking about running water through the engine cooling system. Its a closed system. The coolant is in the heat exchanger.

It always has coolant.

We rent cranes, you have very little time to do any checks before the next boat is being dropped in your spot.

In my case, I can't winterize the engine in my slip, then start it up and sail over to the crane location. Its not winterized anymore. To avoid this, I could close the raw water intake, but then I'm running the engine dry again
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Old 26-11-2020, 08:08   #6
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Re: Can you run a Marine Diesel without Water ?

Other than the impeller (as mentioned) the biggest risk is overheating and for a less-than five minute run, it will be fine. It doesn’t matter whether it’s diesel or gas.

It’s generally called “coolant”. The reason why is because it cools the engine. If the engine is not hot, then there’s nothing to cool, hence thermostats. If the coolant goes through the engine too fast, then it won’t cool, hence thermostats.

And overheating doesn’t necessarily kill your engine immediately, as you mention on YouTube videos. It mostly just causes a shorter life of the engine, and often it doesn’t even do that. If you had a big enough fan, you wouldn’t have internal fluid (think about many motorcycles and the old VWs).

The cooling systems of engines today is highly engineered on port sizes and flow locations to maximize the stability of the system, reduce the noise, etc. but the basics in any “water cooled engine” is very simple and the purpose is the same as if you ran a water hose on the outside of the engine to keep it cool.

You don’t want to overheat an engine just to be overheating it, but you should be fine.
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Old 26-11-2020, 08:21   #7
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Re: Can you run a Marine Diesel without Water ?

I’m not certain I understand what you are asking but I’ll give it a go:

I’m assuming you are talking about an engine with a heat exchanger which has two cooling loops, the ‘freshwater’ (coolant, ethylene glycol) closed loop and the ‘raw water’ (seawater) loop that is used to cool both the engine coolant and the exhaust.

If you want to run without raw water:

1. People talk about ‘suction’ destroying their raw water impeller immediately if they start the engine with the intake seacock shut.

2. The impeller will be spinning fast in a dry pump body- that seems bad, pieces of impeller can clog your heat exchanger etc.

For those reasons it might make sense to disable the raw water pump (belt or impeller removed) to avoid raw water pump damage.

Additionally the other job of the seawater is to cool the exhaust. My exhaust with fiberglass muffler and rubber hose certainly wouldn’t love hot exhaust gas, but in the other hand I believe most purpose-made wet exhaust parts are spec’d to handle a few minutes of dry runtime.

The engine itself shouldn’t care at all as long as your actual coolant loop never gets too hot.

Also- don’t winterize your raw water loop with toxic ethylene glycol, use the non toxic pink stuff and don’t worry about blowing it out into the water on launch.
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Old 26-11-2020, 08:39   #8
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Re: Can you run a Marine Diesel without Water ?

Quote:
Originally Posted by fireman182 View Post
I agree with you.

In my case, a bucket of water would work if I could get my hoses off. This year because of covid power was shut down

I need a heat gun to disconnect hoses.

Do you know how long an impellor can last before it would melt? or its RPMs?
many wooden boats that leak a lot,tee into the suction hose with a valve and length of hose that will reach the bilge.
the engine can be run on the hard using a bucket,or used as an emergency bilge pump
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Old 26-11-2020, 08:43   #9
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Re: Can you run a Marine Diesel without Water ?

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Originally Posted by leboyd View Post
Other than the impeller (as mentioned) the biggest risk is overheating and for a less-than five minute run, it will be fine. It doesn’t matter whether it’s diesel or gas.

It’s generally called “coolant”. The reason why is because it cools the engine. If the engine is not hot, then there’s nothing to cool, hence thermostats. If the coolant goes through the engine too fast, then it won’t cool, hence thermostats.

And overheating doesn’t necessarily kill your engine immediately, as you mention on YouTube videos. It mostly just causes a shorter life of the engine, and often it doesn’t even do that. If you had a big enough fan, you wouldn’t have internal fluid (think about many motorcycles and the old VWs).

The cooling systems of engines today is highly engineered on port sizes and flow locations to maximize the stability of the system, reduce the noise, etc. but the basics in any “water cooled engine” is very simple and the purpose is the same as if you ran a water hose on the outside of the engine to keep it cool.

You don’t want to overheat an engine just to be overheating it, but you should be fine.
I think we're getting terminology mixed up.

I'm talking about anti freeze for the raw water system. Or running the engine with no water from the intake (that cools the coolant and engine)

I am calling the stuff that prevents systems from freezing up, Anti freeze. Same stuff we use to winterize the engine, plumbing etc.

If it was to cool the engine, I would call it coolant.

It is the same stuff however
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Old 26-11-2020, 08:47   #10
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Re: Can you run a Marine Diesel without Water ?

I do it often, when winterizing, if any repairs / mods were done, and before launch in the spring. Especially pre launch. I always start the engine prior to the travel lift arriving to make sure it will start. Would be kind of embarrassing and maybe expensive sitting in the launch well with a no start. I also always remove the impeller for the winter so it doesn't take a set, and of course replace if needs it. With the impeller out, it's safe to run for a few minutes, the coolant will keep the temp low enough. I usually don't go five minutes, maybe a minute or two. If it runs smoothly that long I'm pretty confident it will get me to the mooring. After running I put the impeller back in and we're ready to go. When winterizing I already have the intake hose in the af bucket so it's not really running without water. I change the oil before haulout so in the water warming up for that.
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Old 26-11-2020, 09:25   #11
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Re: Can you run a Marine Diesel without Water ?

Quote:
Originally Posted by atoll View Post
many wooden boats that leak a lot,tee into the suction hose with a valve and length of hose that will reach the bilge.
the engine can be run on the hard using a bucket,or used as an emergency bilge pump
This is pretty awesome. I never thought of that.
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Old 26-11-2020, 09:29   #12
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Re: Can you run a Marine Diesel without Water ?

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Originally Posted by chris95040 View Post
I’m not certain I understand what you are asking but I’ll give it a go:

I’m assuming you are talking about an engine with a heat exchanger which has two cooling loops, the ‘freshwater’ (coolant, ethylene glycol) closed loop and the ‘raw water’ (seawater) loop that is used to cool both the engine coolant and the exhaust.

If you want to run without raw water:

1. People talk about ‘suction’ destroying their raw water impeller immediately if they start the engine with the intake seacock shut.

2. The impeller will be spinning fast in a dry pump body- that seems bad, pieces of impeller can clog your heat exchanger etc.

For those reasons it might make sense to disable the raw water pump (belt or impeller removed) to avoid raw water pump damage.

Additionally the other job of the seawater is to cool the exhaust. My exhaust with fiberglass muffler and rubber hose certainly wouldn’t love hot exhaust gas, but in the other hand I believe most purpose-made wet exhaust parts are spec’d to handle a few minutes of dry runtime.

The engine itself shouldn’t care at all as long as your actual coolant loop never gets too hot.

Also- don’t winterize your raw water loop with toxic ethylene glycol, use the non toxic pink stuff and don’t worry about blowing it out into the water on launch.
This is exactly what I'm talking about.

I didn't think of the exhaust aspect of it. That's a very good point.

Regarding the impeller, how fast does it actually turn?

It takes awhile to empty a bucket of water. For the heat to build up and cause a the impellor to break/melt I would image that would take some time.

They fail with water while the engine is running so I suppose anything is possible
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Old 26-11-2020, 09:30   #13
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Re: Can you run a Marine Diesel without Water ?

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Originally Posted by capt jgw View Post
I do it often, when winterizing, if any repairs / mods were done, and before launch in the spring. Especially pre launch. I always start the engine prior to the travel lift arriving to make sure it will start. Would be kind of embarrassing and maybe expensive sitting in the launch well with a no start. I also always remove the impeller for the winter so it doesn't take a set, and of course replace if needs it. With the impeller out, it's safe to run for a few minutes, the coolant will keep the temp low enough. I usually don't go five minutes, maybe a minute or two. If it runs smoothly that long I'm pretty confident it will get me to the mooring. After running I put the impeller back in and we're ready to go. When winterizing I already have the intake hose in the af bucket so it's not really running without water. I change the oil before haulout so in the water warming up for that.
Agree with all your points! Good advice Thanks for the input
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Old 26-11-2020, 09:36   #14
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Re: Can you run a Marine Diesel without Water ?

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Originally Posted by jt11791 View Post
Without water, you will melt your water pump impeller. Otherwise, no problem for short runs, just don't let it overheat. It's common to let the engine suck from a 5gal bucket of water for short runs on the hard.
What he said. I happen to have a fifty gallon water tank (portable) it can suck from, which makes run time longer. But running without water will destroy the impeller. Ask me how I know....;-)
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Old 26-11-2020, 09:58   #15
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Re: Can you run a Marine Diesel without Water ?

I don't see mention that running dry can compromise the raw water pump seals, which happened to me, so +1 for disconnecting the belt before doing so.
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