Engine ran dry

[Glyka]

Hi,

I used to leave the engine's sea cock always open, until a month ago a friend of mine had to lift his boat off the marina's bottom.

Since then I always close all sea cocks when leaving the boat and have twice ran the engine dry! The last time (yesterday), for about 20 mins. (I hadn't read the excellent idea of leaving the engine keys by the sea cock!!!). I started the engine, performed a place change manoevre (ordered by the marina HQ), left it running until all mooring lines were correctly set, and swiched it off, happy for my perfect move. Half an hour later a (very big) bell rang. Sweating all over, I checked the sea cock and found it closed... Without any thought, I opened it and started the engine. Oddly enough, after a couple of seconds water started to flow from the correct point (the exaust, that is). I switched the engine off, closed the sea cock, left the boat and went home where I could think and cry undisturbed.

The question is: what might the damage be?

The engine is a Yanmar 3HM35F (fresh water) with about 1000 hrs. What I think could be seen as sort of good news is that the fresh water circuit is passing trought a water heater that is usually full of cold water.
I haven't been to the boat since, and I would appreciate any ideas on what to look for (other than the impeller that I will replace anyway) when I will feel brave enough to face my engine.

Thanks,

Theodore


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[Talbot]

IMHO the exhaust area is the one most likely to have suffered damage as it was running without cooling water, whereas the engine was being cooled by the fresh water, so you probably have not done any damage to the engine itself. With a place change in the marina, you would not have been running with high revs, so the engine would have been running cool anyway.

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[Robin]

The impellor will need replacing for sure as you said, otherwise you may have had a narrow escape depending on the time it was running, presumably the alarms (fitted?) for water temp did not go? The other potential for damage would be to the rubber exhaust pipe which of course is designed to have water flowing through it!



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[tcm]

i wil bet money that you are ok. I ran engines dry ( one of them anyway, 400hp) once and alarms ring when you apply real load, not a pottle around the marina. It all seemed ok.

for real worry merchants, get a big sign that say "seacocks are shut NO ENGINES" or whatever - then put in on the dashboard. Otherwise nobody else can use/move the boat if there's a fire three boats down. esp if the marina have the key to your boat. But it would be okay anyway, as above, a bit. So pull yourself together and stop crying!

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[LORDNELSON]

Hi Theodore,
You are not alone in your misdeeds! Last year I motored out of Newport, Isle of Wight, and about ten minutes down the river my wife said, "whats the matter with the exhaust - it is blowing out lots of steam?". Quick move of skipper to turn on water to engine. Our engine is a 35 HP Yanmar with direct cooling. I continued motoring down the Medina with the usual amount of water coming out of the exhaust and since all seemed well did not change the impeller until the end of the season when the usual oil, filters, and impeller change was done. The old impeller appeared in perfect condition and showed no sign of going too soft or loosing adhesion to the boss. The engine itself has showed no signs of distress caused by ten minutes of dryness. Hope this helps! Barry

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[longjohnsilver]

If you've still got fresh water in your header tank then all should be fine, just check the impellor. Even if you've lost some water then probably still all OK, just give it a run, check temperature and oil pressure, if all normal then don't worry.

As already said also check exhaust hose. I have a mate who trying to be helpful a few years back arrived at the boat about half an hour before me and decided to warm the engine without turning on the seacock for about 20 minutes. Because it was not run at load it never reached anywhere near normal operating temperature and consequently not a drop of freash water was lost and no damage to either the impellor or exhaust hose.

So don't worry unnnecessarily!

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[philwebb]

Dont worry, it takes longer than 20 mins to do any damage to the engine. I have a dymo label under the ignition switch that says " Is the cooling water on?"

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[brianhumber]

As you have fresh water cooling the spaces around the cylinder heads will have been unaffected unless you were producing so much power this water got so hot it turned to vapour - pressure would rise and the rad cap release into bilge. From your description this most certainly did not happen.

Remove the impellor, it is still working as it pumped as soon as the seacock was opened but some damage might have been done to tips and it will have got quite warm.

The exhaust hose will have also got hot and this is more difficult to check as the inner layer might have delaminated at the engine end. However you were not running at anywhere near full load so this is a very remote possibility I would suggest.

To stop this in the future try to learn how the exhaust sounds, it will be different with no water. Whilst you will not forget to open the cock again, I notice far more weed at sea is about in recent years which could block your filter up if doing long passages under motor.

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[extravert]

I forgot once when I first owned an inboard diesel engine, and no harm was done.

Another way to not forget in the future is to get into the habit of checking the cooling water is flowing properly every time you start the engine by a quick look over the side. It's good practice to do this anyway.

<hr width=100% size=1>One day, I want to be a real sailor. In the mean time I'll just keep tri-ing.

 

[tcm]

Re: new impeller needed?

um, not so sure it is? From some posts hereabouts the refit of impellers causes more damage than is worth. Run the engine again, if water comes out and the engine temp seems ok and then gingerly fondling the impelller housing means that area is fine.

Note there's less load on the impeller when seacocks closed than withem open -not pumping anything, just churning hence large fans are always started with gates/valves shut - the only issue is the temp of the water in the inlet which ain't getting too hot if the engine is on tickover and the block is cold, as happened here. The damage would be to the block/rings/pistons/cylinder/head/gasket - where the heat was generated. An oil change might be more appropriate?

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[MartinGPerry]

Because no cooling water was being injected into the exhaust elbow this will have got very hot.
Check carefully the hoses that inject the sea water into the elbow - and in particular check the connection where the hose joins the elbow. At the very least the jubilee clips wil need tightening up, if the hose is PVC then I would replace it because it wil have softened and distorted




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[AndrewB]

After the impellor and exhaust hose, next thing likely to go is the head gasket. When that happens, chances are you'll see smoke out the exhaust and a loss of power.

As others have said, with a heat-exchange system you might get away with 20 minutes at low revs just cooled by the circulating FW. If the very big bell that rang is your temperature alarm, then essentially you will have. That's what they are there for - to warn that its getting a bit on the hot side, not as you feared like an oven timer to announce that all is now cooked. You might still have damaged the raw-water impellor, but at least you saw water coming through afterwards, so its probably OK (but worth checking, easy enough to replace).

If the bell to which you referred was simply a mental one, can I recommend fitting a temperature alarm - cheap enough, could save a lot of aggravation in future?

 

[dickh]

The other alternative is to fit a water flow alarm on the inlet hose to the water pump - Halyard do one now which looks a neat job but I believe is expensive - circa £150?? I think. The other way is to fit a DIY alrm using a water flow meter from RS, Farnell or similar distributors - about £20 if I remembery correctly - one job I've been meaning to get round to for a couple of years.

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Glyka]

"can I recommend fitting a temperature alarm"

I think the engine already has one, any good idea on how to check it ? (other than running it dry again, this time for a couple of hours and with full load)


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[Neraida]

Find it, get a thermometer and get the kettle on.
Remove sender thingy and plug hole with finger when realise you are pouring antifreezey water all over your lovely bilges, try to reach screaming kettle with finger in hole, fail.
Search one handed for something to stick in hole (small dutch boys are good for this), end up with hanky shoved in with chart pencil.
Now deaf, switch off kettle.
Get saucepan and pour water into from kettle into it.
Try to find keys to engine for ignition.
Look by seacock and fail to find.
Get coat hanger from hanging locker and bend into shape to fish out keys from under engine.
Turn ignition on and take saucepan to sender unit with thermometer.
Put sender in saucepan and look at thermometer.
Find water down to 65deg c.
Boil kettle again.
Pour new water into emptied saucepan and alarm should wail.

Good luck.

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[Glyka]

Thank you all for your response, advice and support!

I think I saved my head (and, hopefully, it's gasket)

Theodore


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[jerryat]

Hi Teo57!

Agree with Talbot, the exhaust tubing relies on water to keep it cool and prevent delamination or worse. I think I'd disconnect this from the exhaust elbow on the engine and check all is well. Agree with the others re damage to the engine. The short time, with indirect cooling will have given you a buffer and, as it appears the overheating alarm did not operate, it seems you got away with it. Change/check the impeller, lift your eyes skyward, and mumble a humble prayer!!

Good sailing!


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[ted]

Re: new impeller needed?

I had a blockage in the cooling system of my 13.5 hp beta. The alarm came on but we had put it down to an electrical fault. Presently smoke started to come from below so we switched the engine off and arranged a tow in to Pwhelli. Ok the really good sailors would sail in.

It turned out that the extra heat caused the exhaust pipe to go.

According to a recent PBO the temperature of exhaust rises to 400 celcius if you have a coolant problem and is capable of setting a boat on fire.

I arranged for a marine engineer to go over everything as well as replacing the exhaust and hopefully the problem is solved.

I had a new impellor rather than risk the old one.

It is worth remembering that an engine problem puts lives at risk as well as bank balances.

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[Heckler]

Re: new impeller needed?

fresh water cooled, on light load the fresh water circuit would have absorbed the heat as normal and inter cooler would have disipitated the heat almost acting as a radiator.
< The damage would be to the block/rings/pistons/cylinder/head/gasket - where the heat was generated.> the engine didnt overheat, the rad cap didnt blow, the fresh water did what it does under normal circumstances. the only possible damage could be to the uncooled exhaust system
stu

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[brianhumber]

Re: new impeller needed?

Remember the original poster was only running his engine light load so I very much doubt if exhaust got up to the temp yours reached. However many a Hamworthy Air Start compresor ran its ITT/Jabasco circ pump impeller , same design as yours, cause the sea water supply got blocked. ( Old men were not amused when you rang the bridge to tell em only six main engine starts left in the bottles when going through locks on standby)

Whilst tcm is correct in that the pump will be off load with the inlet shut, friction and thus heat is still produced when they are running dry.
As to starting pumps/fans with inlet valves closed I refer readers to the various I of Marine Engineers publications. Basic rule
Displacement pumps -all valves open
Centrifugal pumps - discharge valves shut inlet open
If not I should have never been awarded my 2nd class and combined 1st certificates as i can still remember the oral questions asked during those exams!!

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