Newbie. How to supply more air to my engine compartment.

[rob2]

Unless Michael has made significant modifications, then the engine compartment effectively runs back to the transom and is open to the bilges. Like others, I don't believe a fan will make a jot of difference to the temperature in the engine compartment. Consider how cold the seawater being pumped around the engine starts out - a fan can't match that. Also the engine pumps far more air into the compartment than any fan, admittedly by ingesting it, but it will cool anything in its path.

I guess if it concerns you, you could fit a blower and duct it onto the alternator as that is the component most susceptible to damage through overheating.

Rob.

 

[geem]

Unless Michael has made significant modifications, then the engine compartment effectively runs back to the transom and is open to the bilges. Like others, I don't believe a fan will make a jot of difference to the temperature in the engine compartment. Consider how cold the seawater being pumped around the engine starts out - a fan can't match that. Also the engine pumps far more air into the compartment than any fan, admittedly by ingesting it, but it will cool anything in its path.

I guess if it concerns you, you could fit a blower and duct it onto the alternator as that is the component most susceptible to damage through overheating.

Rob.

I guess it depends on what you have in mind for a fan. My 86hp engine must produce a lot more heat than a 10hp. With the fan off the compartment gets to 60 degC. With the fan extracting from high level in the compartment the temperature stays at 40 degC and that is in the Caribbean. It feels like you are cooking everything in the engine compartment at 60 degC. 40 degC feels a lot more reasonable. I don't see how a suitable fan for a 10hp engine would not drop the compartment temperature appreciably.

 

[Heckler]

Come on Stu! This is a little 10hp donk and has run satisfactorily (just like thousands of others) for 30 years. Nothing unusual about the set up.

As you will see above, the fans fitted to your Benny and my Bavaria do little to (if anything) to reduce engine compartment temperature. They are fitted because of the RCD requirement that originally came from the ABS to remove fumes.

So parsifal is right - current practice has little bearing on the OPs issue, although as I suggested an extractor fan might help with the fumes. Incidentally I ran a little 10hp seawater cooled engine in a confined space for 25 years. Always felt hot down there but never overheated and always able to run to maximum revs. Fortunately not a smelly old Volvo!

Stew
Just did a long reply and lost the lot! Perils of doing it on a dodgy wifi on a Carib beach! The OP had concerns about a hot engine bay. I, along with your self and others, shared our real life experiences with him, some willy waving, one, because of his dislike of me piled in as well. Bottom line, the outlet air from my engine compartment, perhaps because of the location of my boat, can be as warm as a fan heater on low. I often leave the fan on to remove heat from the fabric of my boat, it panders to my engineering sensibilities! So my real life experience is that the fan does remove heat from the boat and if the OP has concerns then fitting a fan can help allay those concerns!
Stu

 

[sailorman]

Hi Guys. Yes you are right I did mean exhaust manifold.
Some of the posters are getting as hot as my engine, I suggest increased lubrication with tea and or alcohol, but the discussion has raised a number of very interesting points.
What I will take away from this is that in my current set up to ensure a greater air supply I could fit some sort of closeable louvre at the top of the cabinet. If the water gets over this I'm in serious trouble.
The question of cooling water volume supplied to the block is an interesting one. I changed the engine water filter to a clear top vetus filter and there does not appear to be any restriction in the supply part of the system. However I don't have any idea of typical volumes that this should be pumping through. It certainly isn't a water festival coming out of the exhaust. But any time I have held my hand over the exhaust the water is not exactly hot so I assume that the flow through of water is sufficient.
With the new louvre in place I will see if there is any appreciable difference in engine cabinet temperature. If not I will have to assume that the problem is not air supply.
The exhaust smoke does have a grey hue to it. I have assumed that this is because the engine is 40 years old.
If I assume that some of the exhaust and cylinder head cooling ports are blocked or partially blocked then it would be nice to do a decoke. Ideally it would be good to do it without removing the exhaust manifold again.
In terms of insitu decoking I have read of people passing some sort of dilute acid through the system. Sounds a bit risky not to mention the discharge into the environment. Anyone got any experience of running any solutions through their engines, and the outcome.

Louvres will allow noise out & prol make no discernible difference the the engine operating temp

 

[NormanS]

There are two times when it's useful to run an extraction fan.
1. To remove any hydrogen from the batteries, prior to starting.
2, After the engine has stopped, particularly applicable for those with smelly engines.

 

[PaulRainbow]

OK, back to the original question and the actual problem, which a few of you seem to have missed/overlooked.

The engine cabinet is very close fitting and I have measured the air temperature after running the engine for short time intervals and it is very hot. Because of the close fitting nature of the cabinet I'm convinced that the engine air supply needs to be improved.

Engine overheating solved, I believe, but engine bay still gets hot and any clothes worn on the boat have a dieselly smell to them.

So, the problems are high air temps in the engine compartment and an ingress of hot/smelly air into the boat. The engine is old and a little worn, burns a little oil but otherwise sounds serviceable, so it's not unreasonable that she smells a bit.

What sensible reason is there to NOT fit a fan to pull some of the hot/smelly air out of the top of the engine compartment ?

 

[PaulRainbow]

There are two times when it's useful to run an extraction fan.
1. To remove any hydrogen from the batteries, prior to starting.
2, After the engine has stopped, particularly applicable for those with smelly engines.

The OP has a smelly engine. What is the negative impact of him running a fan all of the time the engine is running, rather than just when he stops the engine ?

 

[Heckler]

OK, back to the original question and the actual problem, which a few of you seem to have missed/overlooked.






So, the problems are high air temps in the engine compartment and an ingress of hot/smelly air into the boat. The engine is old and a little worn, burns a little oil but otherwise sounds serviceable, so it's not unreasonable that she smells a bit.

What sensible reason is there to NOT fit a fan to pull some of the hot/smelly air out of the top of the engine compartment ?

Finally, common sense!
Answering both posts, do as I suggested before the willy wavers piled in and fit a simple fan using clothes drier hose as a simple ducting, second question, I suspect the power availibilty will preclude the use of a fan when the engine is not running, such as is fitted to my boat.
Stu

 

[Heckler]

The OP has a smelly engine. What is the negative impact of him running a fan all of the time the engine is running, rather than just when he stops the engine ?

I wonder if a olar powered vent?
Stu

 

[lw395]

Hi Tranona sorry I meant 140 F as an idealised maximum engine compartment temp (60 C).
Yes perhaps I should accept that this is how these engines run. I suppose I'm just trying not to run it in a bad way, or a way that will shorten its life

You will more likely shorten the life of the engine by not letting it warm up when lightly loaded.

 

[sailorman]

Hi Tranona sorry I meant 140 F as an idealised maximum engine compartment temp (60 C).
Yes perhaps I should accept that this is how these engines run. I suppose I'm just trying not to run it in a bad way, or a way that will shorten its life

A 40 yr old raw water cooled boat engine is a very old lady she will be more likely to corrode away than wear out

 

[Jabs]

I have two vents on dorade boxes and an inline extract fan which exits on the transom
In forty ambient this summer I kept the fan(ignition) on for twenty minutes after arrival but still had huge heat soak into the living spaces.

Even with a small engine there is a lot of heat there. Dump it overboard!

Good luck

Tony

 

[Tranona]

Stew
Just did a long reply and lost the lot! Perils of doing it on a dodgy wifi on a Carib beach! The OP had concerns about a hot engine bay. I, along with your self and others, shared our real life experiences with him, some willy waving, one, because of his dislike of me piled in as well. Bottom line, the outlet air from my engine compartment, perhaps because of the location of my boat, can be as warm as a fan heater on low. I often leave the fan on to remove heat from the fabric of my boat, it panders to my engineering sensibilities! So my real life experience is that the fan does remove heat from the boat and if the OP has concerns then fitting a fan can help allay those concerns!
Stu

A fan will draw hot air out - obvious because the engine compartment is full of hot air because it has a hot engine in it. however, it will not reduce the air temperature in the box. So of course the outlet will be hot - it is blowing hot air from the compartment where its intake is sited! As i said 10 hp donks run at 70C so the surrounding air in a confined space will be at or near that temperature.

A fan will make no difference when the engine is running, but may reduce the temperature more quickly when the engine is stopped, as well as removing some of the smell.

 

[stevie69p]

Surely if the fan is drawing hot air out, then that air has to be replaced? And it will be replaced with air from wherever the engine intake is drawing its' air from... i.e. the bilges, which will be cooler air...

 

[oldharry]

I still think this engine is running too hot. My MD7A is the same engine uprated to 14hp so should be a bit hotter. Engine bay heat just isn't an issue . So there is something wrong if OPs engine gets that hot. Many parts of my engine remain below around 45c even after several hours running, although the coolant temperature is normal. These old Volvo's have been donking their way about for generations now without fans to cool them. He needs to find out where that heat is coming from. Its an old engine, why have previous owners not been worried by heat build up if this is normal?

Yes mine smells a bit too. Like old Brit m/cycles they are not 100% oil and diesel tight any more without a lot of attention. I suggest OP overhauls his fuel system, particularly the injector return lines which tend to get neglected

 

[PaulRainbow]

What a fantastic bit of kit these old Volvo engines are.

Where can i get one from ?

I'm going to fit one into a small shed next to my house and run some ducting to each room. If it heats the area around it to 70c and that area can't be cooled by removing the air with a fan it'll be a great way to heat the house. I may even run some ducting to the neighbours too, i'm sure they'd be happy to pay for half the meagre fuel bills.

Must be close to perpetual energy.

 

[Lon nan Gruagach]

A fan will draw hot air out - obvious because the engine compartment is full of hot air because it has a hot engine in it. however, it will not reduce the air temperature in the box. So of course the outlet will be hot - it is blowing hot air from the compartment where its intake is sited! As i said 10 hp donks run at 70C so the surrounding air in a confined space will be at or near that temperature.

A fan will make no difference when the engine is running, but may reduce the temperature more quickly when the engine is stopped, as well as removing some of the smell.

Your physics fu is not strong.

 

[geem]

A fan will draw hot air out - obvious because the engine compartment is full of hot air because it has a hot engine in it. however, it will not reduce the air temperature in the box. So of course the outlet will be hot - it is blowing hot air from the compartment where its intake is sited! As i said 10 hp donks run at 70C so the surrounding air in a confined space will be at or near that temperature.

A fan will make no difference when the engine is running, but may reduce the temperature more quickly when the engine is stopped, as well as removing some of the smell.

 

[No Regrets]

Assuming it's the original engine and has been running in this same installation for a few decades, why change it!? :ambivalence:

 

[Poignard]

Do keep up at the back, he said he fixed the overheating of the engine! (...)

His exact words were "Engine overheating solved, I believe, ...". Perhaps it isn't solved. Perhaps the engine is still running too hot, even though it may not get hot enough to set off the overheat alarm.

Regarding his clothes smelling of diesel, there shouldn't be any smell of diesel. My boat doesn't smell of diesel; neither do most people's. Instead of advising him to install a fan to blow the smell away, you would have done better advising him to clean the engine thoroughly and attend to any leaks in the fuel system.