Can you run a Marine Diesel without Water ?

[Cadence]

Originally Posted by Nico Domino

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.

That sounds like a raw water cooled engine not one with a heat exchanger. If so it is correct if not it isn't.

[chasfgr]

If it's an indirect cooling engine, no problem - but expect to change the raw water impeller, if you run it for more than anout 30'. I've never had a problem with the seals, but much has to do with the pump manufacturer. My experience has been with Jabsco (tough as old boots), Yanmar and Rule (inclined to having the vapours).



With a raw water cooled engine the limit is more like 5'.


In both cases the most likely failure is of the flexible exhaust hose.


I've run engines on the hard with my last 3 motors with no ill-effects.

[Nico Domino]

Originally Posted by Cadence

That sounds like a raw water cooled engine not one with a heat exchanger. If so it is correct if not it isn't.

It is correct to any engine without water in it. Not only that, but the gauge will show the temperature only in the location of the probe.

[CassidyNZ]

Originally Posted by Nico Domino

It is correct to any engine without water in it. Not only that, but the gauge will show the temperature only in the location of the probe.

Yes but if the engine has a closed system with a heat exchanger, the temp sender unit will still be immersed in coolant that is being circulated by the engine’s water pump so readings should be good.

On a raw water cooled engine your assessment is correct. The sender will at some point be influenced by metal temperature but normally by that time the engine is close to toast.

Others have already said . . . . in my experience 2 minutes is already too long if the impeller is dry. Remember that because of the eccentric design of the pump, the vanes are against the pump walls with considerable pressure. Unlubricated rubber doesn’t like this. Just check an ordinary macerator pump which is a very similar pump, the instruction in BOLD lettering is DO NOT RUN DRY. There is a good reason for this.

Others have already said . . . my boat has an FRP pipe section connecting the engine to the exhaust. My impeller failed and this FRP pipe burnt through in way less than a minute. Check the components in your exhaust system, it may be as vulnerable.

Last, if it’s a 4 cylinder Yanmar, the raw water pump is gear driven. Try not to run it with no raw water. It will cost you money. And if anyone has a process of removing an impeller from a 4 cylinder Yanmar that doesn’t destroy the impeller please post that process here

[Nico Domino]

Originally Posted by CassidyNZ

Yes but if the engine has a closed system with a heat exchanger, the temp sender unit will still be immersed in coolant that is being circulated by the engine’s water pump so readings should be good.

On a raw water cooled engine your assessment is correct. The sender will at some point be influenced by metal temperature but normally by that time the engine is close to toast.

Others have already said . . . . in my experience 2 minutes is already too long if the impeller is dry. Remember that because of the eccentric design of the pump, the vanes are against the pump walls with considerable pressure. Unlubricated rubber doesn’t like this. Just check an ordinary macerator pump which is a very similar pump, the instruction in BOLD lettering is DO NOT RUN DRY. There is a good reason for this.

Others have already said . . . my boat has an FRP pipe section connecting the engine to the exhaust. My impeller failed and this FRP pipe burnt through in way less than a minute. Check the components in your exhaust system, it may be as vulnerable.

Last, if it’s a 4 cylinder Yanmar, the raw water pump is gear driven. Try not to run it with no raw water. It will cost you money. And if anyone has a process of removing an impeller from a 4 cylinder Yanmar that doesn’t destroy the impeller please post that process here

If heat exchanger unit, remove the raw water impeller and you can run 15-20 minutes, watch your gauges, if direct cooling, remove impeller and run max5 minutes, ignore gauges.

[JohnHolland]

A marine diesel mechanic told me the same thing...remove the raw water impellor to prevent its damage, then ok to run engine for 5 mins. since the internal coolant system will cool it for a short period, especially if you have engine heated hot water and the tank hasn't been drained...takes a bit of the heat away.
good luck
John

[waterman46]

Originally Posted by Nico Domino

It is correct to any engine without water in it. Not only that, but the gauge will show the temperature only in the location of the probe.

It's a bit sketchy with some confused posts but as I take it, and trying to think logically, the OP does not intend to remove the primary coolant in the engine, the one with antifreeze that circulates through the block, and there is no need to do so as long as a 50/50 antifreeze solution has been used. Unless he lives in Antarctica.

The problem was how to winterize the raw water system.

As mentioned, exhaust temperatures can be a problem, I'd guess even after just one minute with no raw water. I'd go with the non-toxic antifreeze into the raw water strainer as suggested, running engine for about 2 minutes or until it was all consumed.

I know he said he can't remove any hoses, but after running the last time, I would sure try to disconnect or cut and drain the hoses of the vented loop. This will drain most of the water out of the heat exchange, which is your most expensive item in that system. If hoses are so hard to disconnect, dried up and brittle on the hose barbs (usually a problem on the exhaust elbow connection), maybe replacement or shortening is in order. When replacing, make them long enough to cut off a damaged end and re-use next time.

I'm curious what do you do in the boatyard about the water/antifreeze, even non-toxic type, spewing out the exhaust. Is it a problem? I'd not do it while yard foreman is around. Or use cheap vodka.

[Redline452]

Originally Posted by fireman182

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

We don't rent cranes (club has a TraveLift) but my winterizing process is to motor the boat to the lift bay, let it idle as they get the slings in position. Then just before they lift the boat, I open the raw water strainer and pour in two gallons (2x 3.78 L jugs, actually) of pink antifreeze (one will do it, two is cheap insurance). When the last of that has been sucked down, stop the engine and let them lift. Takes but a minute or two (ideally with someone in the cockpit to hit the "stop" button), the pump never runs dry, everyone is happy. Fresh-water cooled 4JH2TE, survived 20+ winters so far down to -30C (occasionally worse). Used the same procedure on my previous 2GM20.

[David B]

Originally Posted by fireman182

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?

No need to remove hoses, just unscrew your raw water filter cap, and put a garden hose in there to keep it supplied.

The impeller - as soon as it is dry, will start to be damaged. We are talking rubber vanes travelling at high speed, un-lubricated, across a metal surface. first heat, then sticky rubber, then torn vanes, or a gooey mess.

If you want to do this sort of thing on a regular basis, then look at introducing a 'Tee' (or even better, a 'Y') piece into the inlet tubing, with a ball valve closing off the new port you have added.

A simple hose connector on the other side of that ball valve, and all you need to do in future, is plug a hose on, turn on the water to a reasonable flow, open the valve, and start the engine - or, introduce a short hose from the valve to a bucket of prepared solution for flushing with antifreeze or 'Salt Away' or whatever.

[CassidyNZ]

Originally Posted by Nico Domino

If heat exchanger unit, remove the raw water impeller and you can run 15-20 minutes, watch your gauges, if direct cooling, remove impeller and run max5 minutes, ignore gauges.

Good luck protecting rubber/FRP water-cooled components in the exhaust for 15-20 minutes. Gauges will not indicate that the waterlift is melting. Others may follow your advice but I know that on my boat, significant damage would result from your suggestion.

[Luv2Sail2020]

You will melt your plastic waterlok muffler with no water going through the exhaust hose at the least. Melt other stuff at the worst.

Removing the impeller does prevent that from being damaged, but as others must have stated previously there are other plastic or rubber items in the raw water system that can melt. As soon as you start the engine any water in the muffler is going to get blown out. Then the hot exhaust gas is going to have its way with that thin plastic container. Or your fiberglass muffler. Whatever is in the line.

[Scott Berg]

It sounds like you're talking about winterization of the engine or genset while the boat is on a hardstand. Yes, we do this all the time but here's how most pros do it and you can mock something up.

Either system works.

Preferred system:

Remove the raw water impeller and replace the cover
Remove the hose from the strainer to the engine and connect it to a pressurized supply of antifreeze (the pink stuff). For a small engine a bucket with a hand pump or submerged bilge pump in the bucket will work; we have a 55g drum with a 5gpm pump attached that we take to the boat

You DO NOT NEED TO RUN THE ENGINE, just pump; till pink stuff comes out the exhaust, stop; same system is great on HVAC,etc.

Small boat system:

Take a 5g bucket and fit a hose in the bottom with a valve; run the hose to the intake to the strainer; GROCO sells custom covers with a hose fitting for this exact process; leave the impeller in place; open valve on the bucket, start the engine, run till pink stuff comes out, turn off engine.

Either work. Running w/o cooling raw water is hard on the impeller and uncooled exhaust (if the boat has flexible hose and plastic mufflers) can cause a fire if run too long.

Hope this helps; we used to go through 4 55g drums a week doing this..s.

[Mickeyrouse]

Damage to the impeller usually means the vanes come off in unpredictably-sized pieces. If the raw water system is totally dry most likely the broken parts will be retained in the water pump, with the hub of the damaged impeller spinning around the blades. Easily located, easily removed. But if this happens, be sure all broken pieces can be accounted for. They can be flushed anywhere from the pump discharge through the hose to the heat exchanger, potentially clogging the heat exchanger, or hopefully washing through there into the muffler and then overboard.
Sure a lot less of a hassle to disconnect the drive belt and the raw water system. Some engines- Perkins/Westerbeke come to mind- have direct drive Sherwood pumps. These will have to be removed to disable the pump, not really much more complicated than de-tensioning the pump drive belt. Don’t forget to drain the heat exchanger with the drain cock and/or the zinc anode port. And there’s water in the muffler too. Hope that has a drain port.
I have not personally experienced seal damage on a dry-running pump but no doubt it could happen.
I would give 5 minutes max running the engine without a pump, depending on engine size.

[Mickeyrouse]

Reading previous posts, idea of simply removing impeller sounds simplest, if the pump cover is accessible.

[rslifkin]

Originally Posted by Scott Berg

Remove the raw water impeller and replace the cover
Remove the hose from the strainer to the engine and connect it to a pressurized supply of antifreeze (the pink stuff). For a small engine a bucket with a hand pump or submerged bilge pump in the bucket will work; we have a 55g drum with a 5gpm pump attached that we take to the boat

You DO NOT NEED TO RUN THE ENGINE, just pump; till pink stuff comes out the exhaust, stop; same system is great on HVAC,etc.

This is extremely dangerous advice. You'll end up filling a water lift muffler far more than it normally would with the engine running, and if the exhaust system design isn't optimal, you could easy flood the engine with antifreeze.


The safe option is to NEVER feed any kind of liquid through the raw water system without the engine running.

Plus, on some engines (like mine), if you're not already planning to replace the impeller, you'd waste a solid hour or 2 per engine by the time you get the impeller out and back in compared to just running the engine to winterize.

Personally, I just run the engines and feed antifreeze into the strainers.