Engine cutting in rough seas

Just a thought......If a big following sea shuvs enough water up the exhaust it can (could) stop the engine. Think of like kids sticking a spud up the exhaust of your car. No exhaust out.....engine stops. Also a weight of water closing the exhaust flap for a long period would give the same effect.
 
I think the answer is simple (baffles or no baffles in tank)- never sail with the tank less than half full. I learned my lesson exiting Cuan Sound into a standing wave and sucked in air. Have always carried spare fuel ever since and never allow tank to fall below half full.
 
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Just a thought......If a big following sea shuvs enough water up the exhaust it can (could) stop the engine. Think of like kids sticking a spud up the exhaust of your car. No exhaust out.....engine stops. Also a weight of water closing the exhaust flap for a long period would give the same effect.

[/ QUOTE ]Yes, it's quite common, see my post above. If there is a flap then you get the potato effect if there isn't you damage the engine. In both cases the engine stops.

I don't understand why everyone persists in talking about baffles and part-full tanks. If it had been a problem of air ingress then it would not have re-started on the key.
 
I don't understand why everyone persists in talking about baffles and part-full tanks. If it had been a problem of air ingress then it would not have re-started on the key.
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Not so. An engine with air in the line, or a partial blockage will cut out under power but wait a few minutes and it will often re-start at low revs but cut out again under power. Most diesels will tolerate back pressure due to "dunking" of the exhaust to an extent although I agree it is wise to avoid it if you can.
 
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An engine with air in the line, or a partial blockage will cut out under power but wait a few minutes and it will often re-start at low revs but cut out again under power.

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But the original poster said:-

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Turned the key and it was away again.

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Doesn't sound like air in the fuel to me. Could be a blockage due to stirring up muck although the OP also says....

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We have just bought a second hand sigma 33 with a new plastic diesel fuel tank.[ QUOTE ]


So does not sound like muck or air to me assuming he's checked the filter and that's clean.

Could be a dodgy governor. In heavy seas the governor gets a lot of use that it wouldn't normally get but that could clear itself anyway.

I'd check everything for cleanliness and then leave well alone. It is a sailing boat, after all. If the engine fails you sail it. If the sea is rough there will be wind.
 
I don't know why "they" started to draw fuel from the top of tanks. With a feed from near the bottom of the tank, and a dirt sump which can easily be drained regularly, 99% of fuel problems would never happen.
 
When almost exactly the same thing happened to me many years ago the cause was a flake of rust in the tank. During choppy conditions I assume that this lifted off the bottom of the tank and neatly lodged itself across the inlet pipe. When the engine stopped it fell off again, so the engine would restart almost straight away and run perfectly. I endured this for some time before realising what it was, after some smaller fragments got in there as well.
 
I think the exhaust would have to be really crap to stop a diesel engine at more than tickover. Most yacht exhausts have quite a lot of volume, and the exhaust gases leave the cylinder in a fairly assertive manner. Its wholely different from preventing a petrol engine from starting.
Rough seas demand a lot more fuel flow so I suspect either air in the fuel or partial blockage somewhere. I have heard of bits of crud being sucked into filters, lift pump valves etc, by the high flow rate, then falling back as the flow stops enabling a re-start.
Likewise an air bubble may prevent the motor getting enough fuel to drive a heavily loaded prop, but provide enough to start on the key in neutral.
The symptoms are a bit like my Impala/St Aldhelms experience, where the engine coughed when most wanted then worked perfectly thereafter.
Also could be faulty lift pump struggling with flow rate.
There was a thread recently about the thimble filter right at the input of the injector pump????
good luck with it.
 
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I don't know why "they" started to draw fuel from the top of tanks.

[/ QUOTE ]The OP has a plastic tank. Rotationally moulded plastic tanks don't usually have a uniform thickness, so it can be difficult to seal openings on the base. That's why most plastic tanks have top-mounted fittings.
 
It is a sailing boat, after all. If the engine fails you sail it. If the sea is rough there will be wind
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Oh yes! And just when approaching a difficult entrance with no room to manouver the engine goes dead..... Useful!
 
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I don't understand why everyone persists in talking about baffles and part-full tanks. If it had been a problem of air ingress then it would not have re-started on the key.
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Not so. An engine with air in the line, or a partial blockage will cut out under power but wait a few minutes and it will often re-start at low revs but cut out again under power. Most diesels will tolerate back pressure due to "dunking" of the exhaust to an extent although I agree it is wise to avoid it if you can.

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It certainly sounds like some junk being disturbed and blocking the tank outlet - but it could also be aeration of the diesel.
I remember well being caught out in a bad blow when hobby-horsing caused diesel frothing - the engine required bleeding each time before it would restart - as you would imagine.

BUT - I once owned a diesel Sierra which developed a small split in the fuel delivery line. The engine would cut-out from time to time (for no apparent reason), and would then re-start after a moment 'resting'. Not a good scenario on the motorway. Retrospective logic suggests that bleeding would have been required, but not so. On one trip the AA were called out three times, and neither they nor several other helpful diesel mechanics could solve the problem, and the car eventually had to be 'recovered'. Eventually I junked the car as being completely unreliable, and it was only when the 'scrappy' pointed out the tiny hose split that the fault was identified. He ran that car without further problems for another 2 years.
 
I thought it was to prevent the whole tank draining if the fuel feed pipe was damaged or loosened before the shut off valve?
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Not really.... because it can still empty itself due to syphoning. Apart from the logic of pvb's point it's done that way to facilitate mounting the tank as low down as possible. Often all the outlets and fillers are in a closing plate on top to facilitate ease of manufacture and provide a removable access for cleaning too. Problem is it does not provide gravity feed making it necessary to maintain a totally sealed system to maintain pump priming. That's why I prefer to have at least a small "day tank" higher than the engine with gravity feed..... self priming under all conditions. The disadvantage is that if you also need a bulk tank in the bilge (best place in a boat due to weight) you have to have a more complicated delivery pump system to get the fuel to the day tank. Often on small engines this is not done to keep the system simple, cheap and uncomplicated.
 
I've got a Beta 25 which I installed 3 years ago with new fuel lines and new plastic tank. About 25hrs after installation, whilst in Holland it suddenly stopped, would restart immediately then stop again and had to be towed to a local marina by a frindly Dutch boat. Even thogh everything was new I replaced the filters and eventually had to phone the Beta man in Ipswich who immediately said 'air in fuel line, tighten all joints and bleed at the injectors one by one' I did this and had no more trouble since. He said that Beta engines can get an 'air bubble trapped in the injector' and need each injector 'cracked' whilst running to get rid of this bubble. (After normal bleeding).
 
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Sounds like crap in the tank, stirred up by bad weather and sucked into inlet. When engine stops suction on pipe stops hence engine restarts.
Suggest thorough cleaning of tank, Separator and replace primary filter.
OOPS tabernacles is a better description than mine

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Had a car that did that .... previous never used to fill tank right up. I came along and filled it up. When we dismantled the tank - it had rust flakes from top of tank sitting on bottom doing exactly what you describe.

Here we have a plastic tank on his boat - maybe crud right under pick-up, but if its only when tank is near empty - then it's IMHO an unbaffled tank and allowing air into the pick-up pipe when boat pitches. Because engine is still running for a bit it pulls fuel again behind the air. Engine cuts on air ... but fuels there for start ... ?? Maybe ??
 
A day tank is probably the way to go on a long distance cruiser, less appropriate on a cruiser racer, where the main tank will only be 10 or 20 gallons at most, often 5.
It's also more connections to go wrong, plus a transfer pump needed etc.
My plastic tank had really nasty connections in the top, basically a plastic elbow shoved into what looked like a wiring grommet. They put them in the top because they are only diesel-tight when new imho!
I replaced with some bulkhead fittings from RS IIRC.
 
Phew!!! over six hundred people read my question and thirty six replies, thats more than the "Acetone" question a few days ago!!!! Thanks for all the suggestions. We have our hands full at the moment just getting this baby afloat so our short term solution IS to keep the tank full and at the end of the season if we have any money left (unlikely) have a rethink! NIK
 
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