testing diesel engine ashore

[cladwalk]

I am putting my oceanranger back in the water next week
the yard are stressing that they are busy and to make sure the engine works before hand
would I do any harm by ramming hose up the sea water intake and firing her up for a few minutes?

 

[vyv_cox]

Pressurising it with a hosepipe can give problems. Better to fill a bucket in the cockpit with water then take a hose from the pump to it.

The problem with the hosepipe, and with continuing to pump water in if the engine doesn't start, is that the water will accumulate in the exhaust and can backfill the engine. Don't let water flow through until the engine fires.

If you have a Vetus type strainer with a large lid you can do like this. Use a hosepipe with a trigger attachment. Take the lid off the strainer and fill with water before trying to start the engine, to lubricate the pump. Then leave it until the engine starts, upon which you can squirt water into the strainer. It's quite easy to keep it topped up for a short time.

 

[RivalRedwing]

1) Most yards are not keen on starting engines out of the water (vibration causing props to slip etc), your insurers might have a view too.
2) There is always the risk of flooding the engine with water via the exhaust valves if you turn the water on in advance of starting the engine.
3) What have you done to the engine over the winter that might prevent it from starting? All a diesel needs is fuel, power for the starter motor and air. If you have not changed fuel filters ashore and introduced some air then fuel should be ok an all there really is to worry about is making sure there is enough juice in the batteries.
4) If you are worried about minor electrical issues then a brief flick of the igntion key will momentarily engage the starter and confirm all is ok without the need to start the engine.
Above all assumes the engine isn't a basket case and the yard are not talking code for 'it is time for a new engine sir'

 

[Tranona]

1) Most yards are not keen on starting engines out of the water (vibration causing props to slip etc), your insurers might have a view too.

Minimal risk with a flexibly mounted multicylinder engine. Would be worried about the standard of propping if it could not cope. If the boat is on a steel cradle with the keel on the ground or in a channel then the risk is probably nil.

Just make sure there is not a pristine newly polished boat behind the exhaust!

 

[RichardS]

You only want to check that the engine starts OK and there is surely plenty of thermal capacity in the engine block and water circulating system to start the motor and run it for 10 seconds without any raw water connection.

I've often run outboards and car engines in this situation for a short time and, although I don't know as much about diesel engines, they can't be that different.

Richard

 

[Cymrogwyllt]

You only want to check that the engine starts OK and there is surely plenty of thermal capacity in the engine block and water circulating system to start the motor and run it for 10 seconds without any raw water connection.

I've often run outboards and car engines in this situation for a short time and, although I don't know as much about diesel engines, they can't be that different.

Richard

+1

 

[vyv_cox]

You only want to check that the engine starts OK and there is surely plenty of thermal capacity in the engine block and water circulating system to start the motor and run it for 10 seconds without any raw water connection.

I've often run outboards and car engines in this situation for a short time and, although I don't know as much about diesel engines, they can't be that different.

Richard

Did they have plastic exhaust systems? If all goes well the plastic trap will probably survive. If there is a minor problem like a diesel leak for example, it is only too easy to forget that there is a 10 second limit.

 

[Aja]

Say bye bye..

You only want to check that the engine starts OK and there is surely plenty of thermal capacity in the engine block and water circulating system to start the motor and run it for 10 seconds without any raw water connection.

I've often run outboards and car engines in this situation for a short time and, although I don't know as much about diesel engines, they can't be that different.

Richard

Be prepared to spend some time fishing about for a ruined impeller....

 

[RichardS]

Be prepared to spend some time fishing about for a ruined impeller....

I'm happy to bow to greater knowledge but surely impellers must be more robust than this?

It's not that unusual for diesel engines to overheat because of a blocked or restricted raw water inlet but surely this does not always destroy the impeller?

An engine under these overheating conditions would be stressed far more than running from cold for 10 or 15 seconds on land.

Richard

 

[scottie]

Put the bucket in the saloon or it may syphon into the engine when you stop it

 

[john_morris_uk]

Be prepared to spend some time fishing about for a ruined impeller....

Just take the impeller out first?

Its what we do. Sometimes I shut the seawater inlet seacock and top the seawater filter up with water. Its above the water line and acts as a mini header tank for the engine. If the engine is running at idling speeds, I csn keep topping the inlet filter container up with the kettle and this allows me time to check the engine etc.

Sometimes I just don't bother and start it for a few seconds to check all is ok. There's no chance of it over heating in the first minute or two - but I don't give it that long!

 

[SAMYL]

I'm happy to bow to greater knowledge but surely impellers must be more robust than this?

It's not that unusual for diesel engines to overheat because of a blocked or restricted raw water inlet but surely this does not always destroy the impeller?

An engine under these overheating conditions would be stressed far more than running from cold for 10 or 15 seconds on land.

Richard

If the engine is being started to test it and it is 'dry' and has been for some time then your impellor has a half life of only a few seconds.
If there is some water in the system from before then you may be OK but don't count on it!

 

[Marsupial]

this how we used to it back in the mists of time

take a bucket and suspend it under the boat next to the exhaust outlet (it will catcth water)

fill the bucket with water from a hose or another bucket

take a hose from the engine raw water pump inlet and dip it in the water (if you have a non strainer type skin fitting just ram a pipe into it.

start the engine and top up the bucket from a hose or another bucket as it empties -roughly 10 ltrs ish

you now have a "cooling system" that recirculates the water and will last for about 30 minutes until all the water gets too hot, you could just keep adding water to the bucket to provide more cold water to prolong this time

 

[eagleswing]

running engine on land..

running for 30 seconds without water will fry your raw water pump impeller. you must insure that you have a water source into your raw water pump via filling the strainer with a hose, AND a water source to lubricate the cutless bearing located within your p strut , which is normally lubricated by flowing water. and since most shafts (except the dripless PSS style) rely on water drips to lube the prop shaft, you should also figure out how to supply water to lube the shaft. all in all a lot of aggravation , having 3 friends handle water hoses merely to humor your haul in men..

if your engine worked when you hauled the boat , and your start battery is well charged, no reason it won't start right up in the water. i suspect the r eaosn the yard men want you to start your engine out of water is that if it doesnt start in the slip, they and you have to get it moved away to accommodate the next boat...

 

[john_morris_uk]

running for 30 seconds without water will fry your raw water pump impeller. Either take it out - or put some grease on it then! You must insure that you have a water source into your raw water pump via filling the strainer with a hose, AND a water source to lubricate the cutless bearing located within your p strut , Why? - just don't put the engine in gear! which is normally lubricated by flowing water. and since most shafts (except the dripless PSS style) rely on water drips to lube the prop shaft, you should also figure out how to supply water to lube the shaft. I dispute this assertion. Firstly shafts don't need lubricating continually - you could wet it and allow it to turn over for a few moments if you really need to check the gear box still engages. Better still, just don't put the engine in gear. all in all a lot of aggravation , having 3 friends handle water hoses merely to humor your haul in men.. See above - a little hyperbole here perhaps?

if your engine worked when you hauled the boat , and your start battery is well charged, no reason it won't start right up in the water. There might be lots of reasons: he might have serviced the engine, or he might have worked on the fuel line etc. i suspect the r eaosn the yard men want you to start your engine out of water is that if it doesnt start in the slip, they and you have to get it moved away to accommodate the next boat...

Nothing like writing things down to make them true. Lots of people read these forums, and hopefully most read between the lines....

Speed seals come with some glycerine or something similar grease type gell to put on the blades of the impeller. I have used this in the past but now I just put some water proof grease on the impeller when I am refitting it. I wouldn't run the engine for long with the impeller greased in this way - eventually the grease will dissipate and the impeller might eventually be damaged, but checking the engine starts and runs for a few moments is no problem.

When I have wanted to run the engine for longer periods, I have arranged a hose to be permanently topping up a bucket with the water pump inlet hose into the bucket so that the engine can pump water from it. Allow the buckt to be overflowing with water all the time from the hose and the engine tcan then take as much as it wants or needs. You get water everywhere from around the bucket and out of the exhaust, but you can run the engine for as long as you like.

I think its perfectly reasonable and seamanship like to check the engine runs before you launch. Its what nearly everyone does at our layup facility. In fact I think its part of our terms and conditions that you check the engine before launch as we all share the cost of the crane and delays at launch time would be expensive.

 

[vyv_cox]

Perhaps I should repeat what I said earlier, as my point seems not to have been made. A failed impeller is inconvenient. A failed exhaust could be fatal. Running the engine without water, even if the impeller is taken out, could well cause the exhaust trap to melt. It doesn't take very long for this to happen. A small melted hole could be releasing exhaust gases into the boat without your knowledge.

About 10 years ago I was motoring into Scheveningen harbour. As I passed between the outer lights my engine overheat alarm came on. We had been sailing until then but sails were now down and there was very little wind inside the walls. Unable to stop where I was, as this is a busy harbour, I continued motoring for about 30 seconds to one side of the entrance, then stopped the engine, anchored and replaced the impeller. This fixed the immediate problem, but on investigation later I found that the trap had melted.

It could be that this was the same situation as starting an engine in the yard. The engine had only been running for five minutes or so and the impeller failure may have occurred because the pump did not prime on startup.

 

[Gk 66]

There are some very nervous engine owners here.
The OP only wants to give himself a confidence check that his engine will start on lift in.
Provided that:
The boat is well chocked
The exhaust system has not been dismantled
He does not put it in gear

He will be perfectly safe to start the engine for 30 seconds without wiping the impellor.
Think how long it takes for your circ water system to prime when you start the engine. The impellor doesnt fail then does it?

The exhaust water trap will still have water in it from the last time the engine was run. On my vetus model it is even possible to check this with a torch shining against the side of it.

If you need to run it for longer then fill the top of the raw water strainer with a hose while the engine is running.

If you still have any doubts, than any decent marine engineer will happily consult with you on this for a reasonable fee.(Its something that gets done quite often in commercial boatyards.

In the maritime industry, its quite normal to run a boat engine dry for several minutes whilst launching/recovering from davits.

I'll stand by for incoming, but please dont expect me to be here to reply on a nice day like today!

 

[The engineer]

I have to agree whole heartedly with Vyv. Yachts do tend to have plastic in the exhaust system whch will melt with the temperature of hot exhaust gases pretty fast. I have seen a fibreglass seperator de-laminate and burn from a wet system running dry for a few minutes as the result of impellor failure. The seperator subsequently leaked water and gas into the engine after impellor replacement.
Look after your impellor and don't abuse it, the consequence of failure can go way beyond a few quids worth of rubber.
Rig up a non pressurised water feed to the engine for testing. If the boat has been dry all winter it is worth lubing the impellor before start.

 

[john_morris_uk]

Perhaps I should repeat what I said earlier, as my point seems not to have been made. A failed impeller is inconvenient. A failed exhaust could be fatal. Running the engine without water, even if the impeller is taken out, could well cause the exhaust trap to melt. It doesn't take very long for this to happen. A small melted hole could be releasing exhaust gases into the boat without your knowledge.

About 10 years ago I was motoring into Scheveningen harbour. As I passed between the outer lights my engine overheat alarm came on. We had been sailing until then but sails were now down and there was very little wind inside the walls. Unable to stop where I was, as this is a busy harbour, I continued motoring for about 30 seconds to one side of the entrance, then stopped the engine, anchored and replaced the impeller. This fixed the immediate problem, but on investigation later I found that the trap had melted.

It could be that this was the same situation as starting an engine in the yard. The engine had only been running for five minutes or so and the impeller failure may have occurred because the pump did not prime on startup.

Golly Vyv, Your exhaust must run hot. I have run our engine several times without water - albeit for only a few minutes and it hasn't melted anything. For a while I did worry about the water trap, and always checked the temperature of it and for leaks. I had it out of the boat a few weeks ago and checked the inside baffles etc and it was fine. I suppose its cooled from the water that is still in it from the last time it was run in the sea.

 

[vyv_cox]

Think how long it takes for your circ water system to prime when you start the engine. The impellor doesnt fail then does it?

Priming of the raw water pump is pretty much instantaneous. Don't know what you mean by the 'circ water system' but no other pump on board has an impeller like the raw water pump.

The exhaust water trap will still have water in it from the last time the engine was run.

Not if you have drained it, as you should, to prevent frost damage.

If you need to run it longer then fill the top of the raw water strainer with a hose while the engine is running.

Which I said earlier but you are not going to set that up in seconds, are you? Set it up beforehand and do the job properly.

In the maritime industry, its quite normal to run a boat engine dry for several minutes whilst launching/recovering from davits.

Nonsense. I have seen lifeboats that did but they didn't have impeller pumps.