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Condensation in the engine compartment.


Neil2

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During the Winter (and only in the winter) I get a build up of condensation on the exposed steel surfaces of the engine compartment which creates a small pool of water in the bilge. It's only about a litre every six weeks or so but it's annoying nonetheless. I've tried leaving the engine room exposed when the boat's unattended and sealing it up completely and neither approach seems to have any effect.

 

I'm wondering whether fitting some sort of fan/blower would help, I could have this on a timer from the shore power, or does anyone have experience of insulating the engine room?

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Not surprising really given the huge amount of cold metal there is in an engine room/ ,ole I suspect that you are not alone with this issue (I have it too)

Phil

I think Phil is probably right. I get it in my trad stern with no outside openings which is bone dry outside of very cold weather. It would be interesting to hear from anyone who doesn't have this issue to identify what, if anything, makes the difference.

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I think Phil is probably right. I get it in my trad stern with no outside openings which is bone dry outside of very cold weather. It would be interesting to hear from anyone who doesn't have this issue to identify what, if anything, makes the difference.

I did have it in my trad stern engine room but since buying a dehumidifier it has reduced massively.

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I think Phil is probably right. I get it in my trad stern with no outside openings which is bone dry outside of very cold weather. It would be interesting to hear from anyone who doesn't have this issue to identify what, if anything, makes the difference.

We dont get any on our engine or in the engine bay, but we do have huge engine room vents on the side of the boat and the boat is plastic.

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We dont get any on our engine or in the engine bay, but we do have huge engine room vents on the side of the boat and the boat is plastic.

I did wonder if external vents made any difference, not that I'm keen on cutting holes in the hull sides but my engine room, like many, has no outside venting at all which can't help.

 

No doubt a dehumidifier would work but at a cost - I was just thinking about a ten quid fan...

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We have a semi trad and don't get any condensation problems. There are 2 vents one on each side of engine compartment, about 9x6 inch. Ventilation is the best way to start dealing with any condensation problems.

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I did wonder if external vents made any difference, not that I'm keen on cutting holes in the hull sides but my engine room, like many, has no outside venting at all which can't help.

There must be some ventilation or your engine would not get it's required diet of oxygen and your alternator would overheat and die.

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There must be some ventilation or your engine would not get it's required diet of oxygen and your alternator would overheat and die.

Note - I said no outside venting.

 

When we are under way the engine is effectively drawing air from the outside as the hatch/doors are open.

 

The problem arises when she's left in the marina for several weeks and the engine is effectively sealed from the outside air.

 

But it sounds like outside venting might be the answer.

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  • 2 years later...
On 12/03/2015 at 20:07, Neil2 said:

Note - I said no outside venting.

 

When we are under way the engine is effectively drawing air from the outside as the hatch/doors are open.

 

The problem arises when she's left in the marina for several weeks and the engine is effectively sealed from the outside air.

 

But it sounds like outside venting might be the answer.

Did you ever find the cause/cure?

I've removed about 30 ltrs of water from my cruiser stern engine bay.  there was 2" in the bilges either side of the engine, and it turns out the what I thought was oil under the engine is in fact a lot of water (again 2" deep) with a fine layer of oil on top - the bilge under the engine is completely separate from the side bilges so a domestic water leak could not get into this space.

I've dried/cleaned it all out and since the weekend have had no water appear.  We also have an Eberspacher D5W in this bay which has been used daily over the winter and I think this is likely the cause, heating the air inside the bay on very cold mornings for 2 hrs (and evenings), then when that air cools it condenses on the inside of the steel.  

Other possibilities:

- water from the heating system.  Unlikely as no loss of water from the closed circuit.

- water from the engine. Unlikely as I have only needed to put 1/2 ltr into the engine in the last 6 months.

- water from domestic supply.  As above, unlikely as it would not be able to deposit exactly the same 2" depth of water in the engine area.

- Calorifier leak.  This is sat in one of the side bilges but again water cannot get into the engine bilge

- Stern gland.  This barely drips (currently 1 teaspoon a week). 

Other than the above I'm stumped.  I'm going to repaint the bay shortly and also lay absorbent mats about the bay for a few months and check daily to see what, if anything is dripping.

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4 hours ago, Psycloud said:

Did you ever find the cause/cure?

I've removed about 30 ltrs of water from my cruiser stern engine bay.  there was 2" in the bilges either side of the engine, and it turns out the what I thought was oil under the engine is in fact a lot of water (again 2" deep) with a fine layer of oil on top - the bilge under the engine is completely separate from the side bilges so a domestic water leak could not get into this space.

I've dried/cleaned it all out and since the weekend have had no water appear.  We also have an Eberspacher D5W in this bay which has been used daily over the winter and I think this is likely the cause, heating the air inside the bay on very cold mornings for 2 hrs (and evenings), then when that air cools it condenses on the inside of the steel.  

Other possibilities:

- water from the heating system.  Unlikely as no loss of water from the closed circuit.

- water from the engine. Unlikely as I have only needed to put 1/2 ltr into the engine in the last 6 months.

- water from domestic supply.  As above, unlikely as it would not be able to deposit exactly the same 2" depth of water in the engine area.

- Calorifier leak.  This is sat in one of the side bilges but again water cannot get into the engine bilge

- Stern gland.  This barely drips (currently 1 teaspoon a week). 

Other than the above I'm stumped.  I'm going to repaint the bay shortly and also lay absorbent mats about the bay for a few months and check daily to see what, if anything is dripping.

Since that post I have made quite a few changes in the engine bay which included re-routing the exhaust system and fitting a big silencer, I also fitted a load of heavy soundproofing.  I don't get the condensation over the winter now but I do still get it when under way... it now appears on the surface of the uxter plate and I think it's because the rest of the engine room is quite well insulated the uxter plate is the only cold surface.  I'm guessing that when the boat is moving the steel is continually being cooled, unlike when it's at rest.  Also we have moved to a different marina and we haven't experienced a really cold winter since.

30 litres of water seems an awful lot compared to what I was getting, but I have seen cruisers and semi trads in frosty weather with a lot of condensation so I suppose it could build up over time.  My money would be on surface water though, I'd have a really close look at the deck, even a pin hole can be enough to cause real problems.  I once traced a nuisance leak to the tiniest of holes in the weld on a hinged deck lid. 

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On 3/12/2015 at 11:51, Neil2 said:

During the Winter (and only in the winter) I get a build up of condensation on the exposed steel surfaces of the engine compartment which creates a small pool of water in the bilge. It's only about a litre every six weeks or so but it's annoying nonetheless. I've tried leaving the engine room exposed when the boat's unattended and sealing it up completely and neither approach seems to have any effect.

 

I'm wondering whether fitting some sort of fan/blower would help, I could have this on a timer from the shore power, or does anyone have experience of insulating the engine room?

I use Tesco's nappies.

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17 hours ago, ianali said:

Deck boards leaking? Ian.

Sorry, I should have mentioned we have a cap and dodger over the stern at all times and the deck boards remain dry even when there is damp in the bilge.

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A windy ventilator, like the ones you see on top of vans might help.  You would also need a vent to let air in.  But doing this could actually make it worse.  A passive humidity collector is probably a better bet.  Could humid air get in there from the cabin?

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50 minutes ago, tizzy said:

We get it all the time in a semi trad but then isn't that why we have a bilge pump. I have stopped worrying about it.

 

Whoa! You get so much you can pump it!! I thought my damp patch was bad enough.

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58 minutes ago, system 4-50 said:

Whoa! You get so much you can pump it!! I thought my damp patch was bad enough.

Crikey, yeah! When I said a few posts above that I get it, I'm talking about an occasional moist film on the insulated steel side in the engine 'ole when the inside of the boat is warm and the weather outside is very cold. My engine 'ole has a vent either side and it's below the warmer control space inside the trad back doors, so an occasional bit of condensation is probably inevitable. Enough to pump out though? :(

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Any heat source in the unused engine bay like a calorifier or diesel heater will attract condensation. Then there's also the temperature differentials between the air and large lumps of metal like the engine or large volumes of liquid like the fuel tank or even the uninsulated steel of the boat. As the air temperature changes overnight into the day time, the temperature of these greater masses don't change as quickly and can't "keep up" with the ambient temperature. So you might have warm (daytime) air in contact with the cold (overnight) engine and the moisture in warm air in contact with a cold surface will condense. 

Extra ventilation might help but it might not. Just leave some nappies in strategic places.

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