Can you run a Marine Diesel without Water ?

[zstine]

I have removed my impeller and run the engine many times for 5 min. getting air out of the fresh water side after a coolant change was 1 reason. getting air out of fuel lines another.. absolutely no problem as long as you shut down as soon as it gets up to normal operation temp... about 175F in my case.

[jmschmidt]

Done it many times. Just disconnect your raw-water pump (difficult if mechanical, easy if electric or remove impellor) and watch your temp gauge, shut her down when temp starts to climb.

[fireman182]

Originally Posted by goboatingnow

Theres is no harm is running the engine for 30-40 seconds , giving it a few "guns" to expel whatever water might be in the system , there is no need to do it much longer

My winterising consisted of shutting the sea cock and feeding fresh water mixed with anti freeze ( 3:1, -25degree C protection ) through the raw water system ( in this case the engines were big , so about 25 litres was used of mixture ) . Then when that was done and the boat lifted , I started the engines on the hard and " gunned" them for about 15 seconds , this expelled any standing antifreeze . I never tried to drain the raw water as my experience is its very difficult to access certain areas to ensure they drain down

This process was used for 10 years and was successful in surviving two very bad winters where the outside dropped to -15 degree C

Thanks for the reply. I appreciate your winterizing method. Essentially were just replacing water in the engine cooling system with a liquid that wont freeze.

My question is why did you come up with the number 30-40 seconds?

I'm not doubting anything you're saying.

I'm curious to find out what the exact time of impeller failure due to lack of water would be.

Based on YouTube videos of impellers blowing out and spoken legends by local sailors a marine diesel engine at idle could go for up to 15 minutes before over heating and causing issue.

The tales and lore of the dry diesel engine are all over the place

[Cadence]

Originally Posted by fireman182

Thanks for the reply. I appreciate your winterizing method. Essentially were just replacing water in the engine cooling system with a liquid that wont freeze.

My question is why did you come up with the number 30-40 seconds?

I'm not doubting anything you're saying.

I'm curious to find out what the exact time of impeller failure due to lack of water would be.

Based on YouTube videos of impellers blowing out and spoken legends by local sailors a marine diesel engine at idle could go for up to 15 minutes before over heating and causing issue.

The tales and lore of the dry diesel engine are all over the place

Anyone advocation a dry impeller will last 15 min. is blowing smoke up your butt. That's being polite.

[fireman182]

Originally Posted by grantmc

I doubt an impellor would actually melt actually given they're made of a rubberised compound; they're not a type of plastic. When they do die just sort of come to pieces and make a big mess in the heat exchange.

I agree. My question is basically how long will an impeller run dry before it is damaged?

How long can a marine diesel run before over heating?

I know many factors are taken into consideration. At 0- Celsius it takes longer than at 30 - Celsius.

I have come across a common fear of starting an engine on the hard. Just looking into factual validity of this fear

[fireman182]

Originally Posted by Cadence

Anyone advocation a dry impeller will last 15 min. is blowing smoke up your butt. That's being polite.

Not an impeller, but the engine itself.

Local legend has it a sailor dropped his boat a launch during the spring time, failed impellor or no impellor (cant remember) and once in the water he ran his diesel for 15 minutes before he noticed it was running hotter than normal.

[Cadence]

Originally Posted by fireman182

I agree. My question is basically how long will an impeller run dry before it is damaged?

How long can a marine diesel run before over heating?

I know many factors are taken into consideration. At 0- Celsius it takes longer than at 30 - Celsius.

I have come across a common fear of starting an engine on the hard. Just looking into factual validity of this fear

Remove the RW impeller and watch your temp. gauge. I've not had a problem going to normal operating temp. which is measures from the fresh water circulating in your engine.

[boatpoker]

Originally Posted by chris95040

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.

+1 on all this Plus, if you have a plastic waterlift muffler, they can melt pretty quickly with no cooling water.

[zstine]

I have removed my impeller and run the engine many times for 5 min. getting air out of the fresh water side after a coolant change was 1 reason. getting air out of fuel lines another.. absolutely no problem as long as you shut down as soon as it gets up to normal operation temp... about 175F in my case.

[fireman182]

Originally Posted by boatpoker

+1 on all this Plus, if you have a plastic waterlift muffler, they can melt pretty quickly with no cooling water.

Quickly is subjective. Some people say 30 seconds, some say 10 minutes or longer

Like NFPA fire rated walls and doors etc. we know how long a product can survive at a given temperature.

For example a fire separation wall is rated at 4 hours at a certain length of time at a given temperature for fire conditions. (I don't have exact specifics but they are published)

This isn't a guess. The fire rating lenght could be considered quick, it could be considered long depending on how you look at it or if its your house lol

Do plastic water lift mufflers have the same rating?

They must be rated for a certain amount of heat considering their job

[Ziggy]

Originally Posted by fireman182

Quickly is subjective. Some people say 30 seconds, some say 10 minutes or longer

Like NFPA fire rated walls and doors etc. we know how long a product can survive at a given temperature.

For example a fire separation wall is rated at 4 hours at a certain length of time at a given temperature for fire conditions. (I don't have exact specifics but they are published)

This isn't a guess. The fire rating lenght could be considered quick, it could be considered long depending on how you look at it or if its your house lol

Do plastic water lift mufflers have the same rating?

They must be rated for a certain amount of heat considering their job

I have never seen such a rating for a plastic waterlift. Good luck finding it, even if it is rated by someone. The waterlift is the first thing to without raw water cooling. Probably 30 sec to 1 min is pretty safe. But it's easy to supply raw water cooling on the hard using the hose in a bucket method. Added benefit is you flush the cooling system with fresh water. I don't know if it really helps, but it can't hurt.

[roverhi]

I've run my Yanmar 3GM30F without raw water in the heat exchanger for quite a ways longer than 5 minutes. Something got sucked into the intake blocking raw water and didn't realize it till the engine coolant had almost boiled away. Was almost at the slip, added new coolant and powered into the slip with the engine steaming. Replaced the raw water impeller which was missing one vane, cleaned out the intake and everything was good. That was more than 10 years ago and still doing fine. Might want to remove the impeller but for 5 minutes or less it might be okay. Don't try it with an engine with an aluminum head. Aluminum heads warp just talking about overheating.

Have run gas engines without water for short periods without problems. Only engine that died was the result of not enough anti-freeze, despite reading good on a tester, and the coolant freezing not allowing it to cycle through the engine. Drove at least 5 miles on the freeway before the engine blew up.

[Squanderbucks]

Try this. Close the engine sea cock. Open the top of the water strainer if it has a cap and basket. Put a garden hose in the top of the strainer and turn on the water. Run your engine as long as you like. They make a fitting just for this purpose if you have a Groco strainer very handy.

[Cadence]

Originally Posted by Squanderbucks

Try this. Close the engine sea cock. Open the top of the water strainer if it has a cap and basket. Put a garden hose in the top of the strainer and turn on the water. Run your engine as long as you like. They make a fitting just for this purpose if you have a Groco strainer very handy.

I guess that would depend on the engine size?

[Nico Domino]

Originally Posted by fireman182

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?

Just a note, if you run the engine without water, you can bot trust the temperature gauge, as it is not immersed in the cooling water. Air does not transport heat the same as water. The engine will probably be hotter than the gauge shows.