Engine room heat

Mambo42 · Jun 22, 2022

Last November I bought my Defever 49 and obviously the OAT at that time was pretty low, so engine room temperatures were quite ok.

My boat is lying in Greece and summer temperatures can get quite high there. 100 - 115 degrees in August is pretty normal.

In May I spent about 1 month on the boat, mostly familiarizing and doing maintenance, but already then I noticed the engine room temperatures to be quite high.
There are 2 Ford Lehman 120's, plus a 6 Kva generator in the engine room, all of them generating heat.
The engine room does have 2 blowers, but for some reason they switch themselves off after a couple of minutes. No idea if this is normal or why it happens. Have not had the time yet to get to that project.

The engines get their air via inlets on the side of the boat, so no worry about that. But I have no idea where the engine room itself gets any fresh air from, haven't found an inlet yet.

With the temperatures in the engine room already high in May and expecting much higher temperatures in August, I could be looking at temperatures of 160 - 175 degrees inside the engine room while underway.

In the boats I had before this one I never reached temperatures like that, so first question is then: 'is this normal ?'

The second question then relates to the batteries. As far as I know batteries should not be kept in places where temperatures can get higher than 80 - 90 degrees. Yet, the batteries are in the place that is apparently designed for them. In other words, this is where they have been all the time. Can I keep the batteries here or should I move them ?

And last question, is there anything I can do to keep that temperature under control ? Does anyone have experience with engine room temperatures in very hot climates ?

Would appreciate your insights on this one.

Insequent · Jun 22, 2022

I can give you a little insight. My boat is essentially the same size and style although you may have a stand-up ER, not sure? I have 4 hull vents for the ER. The forward ones are set as intakes and have a Delta-T axial fan (9", 700cfm) to assist inflow from that caused from engine aspiration. The rear vents are set-up as exhaust vents for cooling and each has a blower of 200cfm capacity. I run all 4 fans all of the time the engines are running. I strongly recommend that your blowers be configured to run whenever you wish, and that you run them whenever the engines are running.

I am at latitude 27°S, so a sub-tropical climate. In summer ambient temps can certainly get "up there" but in other seasons 25-30°C would be typical air temps. I recently installed LFP batteries in the ER. Their specs say they are not to be charged at temps above 50°C. Before installation I had put a sensor in the area the batteries would be placed and noted that max temps were 47°C in the ER in summer, with ER doors closed and engines at normal cruise.

Next summer I will monitor ER temps (the sensor has bluetooth and I read it from the helm) during cruise and if they start getting close to the battery limit I will open the ER door, or even a couple of the floor hatches, and that should enable the ER to be below the critical temp. Were I doing another refit I would not put the charger/inverter or the batteries in the ER. A bit hard to change it now. But even Fleming have made this mistake. Inverters are typically rated at 25° and de-rate substantially as temps increase. At a boat show a year or so ago and when inspecting a Fleming 58 I asked where are the batteries? The dealer said "outboard of the engines{" and "yes, its a mistake to put them there".

I saw on another thread that you run your engines well below WOT and I think if you adopted similar strategies to me you will be OK.

Mambo42 · Jun 22, 2022

Thanks Brian for this extensive reply. Great insight. I will change the engine blowers for bigger ones and luckily they are connected straight to the fuses. In other words, flip the fuse and they will start to work. The fact they quit after a little while therefore must be a problem. Guess the only reasonable thing to do is change the blowers completely.

I will see if I can get some measurements as well in August, saw that AGM's work well at 20 degrees Celsius, which is about 70 Fahrenheit. Anything above that reduces lifespan of the batteries, so 150 in August is definitely not a good idea.

Thanks again for the insight and I will make this problem one of my priority issues to be solved prior to taking the boat out.

RT Firefly · Jun 22, 2022

Greetings,
While I understand the need and desire for good ER ventilation how can increasing the air flow of air with an ambient (outside) temperature of 100F lower the ER temperature to anything less than 100F? 100F is MUCH preferred to 170F but still...

Relocation of the charger/inverter and the batteries to a cooler location seems to be the only significant option. I suppose, on the other hand, one could always add AC to the ER. Something I always wanted and wished I could do.

SeaDogAK · Jun 22, 2022

Even if the batteries weren’t in the ER, temps that high are a problem if you need to work on anything down there while under way.

Mambo42 · Jun 22, 2022

@ RT Firefly,

The inverter is already in the Lazarette, but the batteries are indeed a problem. I understand I won't be able to lower the temperature to less than 100 in summertime, but 150 is completely over the top.

Already in May going in the engine room after running the engines for a couple of hours, even with the door to the lazarette open and the hatch to the lazarette also open, was a hot experience. The engines are of course running at 170 degrees and they remain warm for hours after you shut down the engines, so they keep heating up the engine room. The moment I switch on the generator I have another heat source in the engine room, it did not make me happy when I encountered it in May.

An airconditioning might be a good solution, great tip. Should not be too difficult to install, I have enough access to cooling water and otherwise I can perhaps go (for now) with a mobile airco. Just dump the waterreservoir in the bilge and let the bilge pump take it out. In October, when we put the boat away for the winter, I can start looking for more fixed solutions to keep the engine room temperature under control.

Mambo42 · Jun 22, 2022

SeaDogAK said:
Even if the batteries weren’t in the ER, temps that high are a problem if you need to work on anything down there while under way.

You are correct, coming in the engine room while underway is not really fun, it is a bit like entering a sauna. That is why I was wondering what everybody else has in temperatures in their engine rooms ? Are they also that hot or is it just mine ?

RT Firefly · Jun 22, 2022

Greetings,

Mr. M. I can't remember exact numbers but our ER would reach in the neighbourhood of 120F without the generator. Twin Lehman as well. I did try running the ER blower while underway but that didn't seem to make much noticeable difference. No idea of the CFM of the blower.

I did NOT have a lazerette or any suitable place to relocate the batteries or the inverter BUT I did give AC some serious thought. Boat is gone now so it's moot.

rslifkin · Jun 22, 2022

I just added temperature monitoring to my ER this season. So far the hottest I've seen underway is 98*, got just over 100* after shutdown. This was with blowers off (they draw from down low anyway, so they only drop the temp a little bit), running at slow cruise, ambient temp in the low 80s, water temp in the high 60s. I'm sure I'll see higher temps as the summer progresses and it would likely get a bit hotter with a long run on plane (which is unlikely to happen at all this year).

Mambo42 · Jun 22, 2022

@ RT Firefly,

Thanks.

So I understand that more boats have high ER temps in the summer. Makes me wonder if they were designed like that or that owners never thought it to be a problem.

Was your temperature with the ER closed or open to the outside while underway ?

Relocating the batteries to the lazarette is not really an option for me. The lazarette is full at this moment. There is the heating system, an extra 100 gallon fuel tank, inverters, dive compressor, the place is packed.

Next year I want to change over to LiFePO4 batteries, which can handle the heat a bit better, but they also have a limit well below 170 degrees. On top of that, indeed working in these hot temperatures is not going to be fun if something breaks down while underway.

That idea of an airconditioning is starting to sound like a very good idea to me. Now I just need to figure out how many BTU I will need, is going to be a lot I think.

jleonard · Jun 22, 2022

The general rule of thumb is no higher than 30 degrees F above ambient air temperature.
When I installed the new Cummins 6bta in my old Mai ship the Cummins tech measured this and documented the results.
(I passed)

Mambo42 · Jun 22, 2022

rslifkin said:
I just added temperature monitoring to my ER this season. So far the hottest I've seen underway is 98*, got just over 100* after shutdown. This was with blowers off (they draw from down low anyway, so they only drop the temp a little bit), running at slow cruise, ambient temp in the low 80s, water temp in the high 60s. I'm sure I'll see higher temps as the summer progresses and it would likely get a bit hotter with a long run on plane (which is unlikely to happen at all this year).

Thanks Rsflikin,

Good to hear other experiences with ER temperatures. Since I just bought the boat last winter I have no hard figures on August / September, but I fear the worst. After experiencing the high temperatures in May already I can only conclude that it is going to be worse.

Watertemps in my area are going to be around 85 - 90 in August / September which means that this is going to be the base temperature of the hull.

Except for the batteries not liking these temperatures I also have all the electrical cables which are definitely not going to like those temperatures. The insulation material is going to dry out, resulting in the need for changing cables much faster.

Mambo42 · Jun 22, 2022

jleonard said:
The general rule of thumb is no higher than 30 degrees F above ambient air temperature.
When I installed the new Cummins 6bta in my old Mai ship the Cummins tech measured this and documented the results.
(I passed)

Thanks for the input JLeonard,

30 degrees above ambient is not what I am having at this moment, so I now know for sure am going to need airco in the ER. I guess this boat was not made for this climate, but the former owner either did not notice it or did not care.

For me it is also a safety issue, so I will address it ASAP.

rslifkin · Jun 22, 2022

Air conditioning the engine room would be a challenge, I think. You'd need quite a lot of cooling capacity (lots of power draw) to get it cold enough. I'd start with more ventilation first. Make sure you have adequate air intake ducts and blowers (let the blowers draw from the top if they're for heat extraction). That'll get you a lot closer to ambient temperature.

As far as engine air intakes, do yours really draw directly from outside? Most draw from inside the engine room, which helps move more air through there for cooling. With mine, I've noticed that if I jump up on plane after running slow for a bit, the engine room temperature actually drops momentarily due to the increase in airflow.

RT Firefly · Jun 22, 2022

Greetings,
Mr. M. ER closed.

Mambo42 · Jun 22, 2022

rslifkin said:
Air conditioning the engine room would be a challenge, I think. You'd need quite a lot of cooling capacity (lots of power draw) to get it cold enough. I'd start with more ventilation first. Make sure you have adequate air intake ducts and blowers (let the blowers draw from the top if they're for heat extraction). That'll get you a lot closer to ambient temperature.

As far as engine air intakes, do yours really draw directly from outside? Most draw from inside the engine room, which helps move more air through there for cooling. With mine, I've noticed that if I jump up on plane after running slow for a bit, the engine room temperature actually drops momentarily due to the increase in airflow.

I have seen that the blowers are almost at the highest point in the engine room, so that part is ok. I guess I will just have to change them since they switch themselves off for some reason. I can't find any information explaining if the former owner had issues as well or that he ever replaced them.

The engine air intakes are on the passage ways next to the salon area. There are 2 on each side of the salon, so assume one is for the engine and the other one is for the engine room ventilation. The engine air inlet is connected to a hose which leads directly to the engine, in other words, the engine does not use air from within the engine room. One additional consequence of that is that I have not found the air filter yet, so that will be up on the list as well. We may have to disassemble the boat for that quite a bit I fear.

The two rear fresh air inlets draw from the outside, but I have no clue where they leave the air. I don't feel any air movement in the engine room when the blowers are on. If those are not air inlets, but outlets then my question becomes: 'where is the air inlet for the engine room ?' So far I have not found it.

As for installing an air conditioning. I have 2 airco's in the salon which we will not be using. We normally live in the Caribbean, are used to a warm climate and during day time we won't be sitting in the salon. Ventilation with all the windows/doors open is good. I don't see myself keeping the doors closed and switching the airco on for the fun of it.

So at least one of those airco's (Dometic) could be moved to the engine room. Even if it won't be able to cool down the engine room back to 70 degrees, if it can keep it at 80 or 90 I will also be happy. Anything better than 150 degrees.

Good part of moving the airco is also that we will regain some storage space in the boat. The former owner placed the airco's in the large storage locker in the salon, which therefore is now unusable. The outlets are under the stairs to the pilot house, which makes that space also unusable for storage. So in all it won't be a bad trade off.

GoneDiving · Jun 22, 2022

Are your blowers designed to actually exchange all the air volume in your ER? Mine aren't as the inlet and exhaust are very close together and at the same height. This allows cooling air to simply travel from one port to another without removing any of the hot air volume. I intent to reconfigure this to have the cold air ducted low on one end and hot air exhaust high at the other end.

See the attached images

Mako · Jun 22, 2022

Mambo, my buddy had a Mainship 34 with twin Lehman naturals. Always running hot. So I helped him to install two small bilge blowers, stuck up inside by the opening. We then ducted the blowers directly to the intakes of the engines. It dramatically lowered the op temperature down to normal levels. Focus on fresh air intake versus hot air exhaust

Mambo42 · Jun 22, 2022

GoneDiving said:
Are your blowers designed to actually exchange all the air volume in your ER? Mine aren't as the inlet and exhaust are very close together and at the same height. This allows cooling air to simply travel from one port to another without removing any of the hot air volume. I intent to reconfigure this to have the cold air ducted low on one end and hot air exhaust high at the other end.

See the attached images

@ GoneDiving

Thanks for your reply, good question and to be honest: I have no idea what the thought was when it was designed.
I bought this boat last October and this is my first Defever, so am truly on a discovery tour through the boat, figuring out what every cable, pipe or tube is for.

What I have found so far is that forward of the fuel tanks there is a thick hose coming from the forward air vents on the side deck and they lead straight to the engines. There is no air coming into the engine room via these air vents.

The rear air vents are aft of the fuel tanks (port and stbd) and there are also a lot of air hoses running there. First there is the thick exhaust hose (about 10 - 12 inches in diameter) and they lead to the lazarette and then out of the exhaust.

Behind those hose are the blowers, so almost impossible to reach. I assume they draw their air from the aft air vents on the side deck, but I have no idea where the exhaust is. When the blowers are on I don't feel a movement of air in the engine room and when the simplest of blower already moves about 300 m3 of air per hour we are talking 10 m3 of air per minute when 2 blowers are on. I should be able to notice that, but so far I haven't noticed any air movement.

Preferably I would like to see the air being drawn in on one side and sucked out on the other side, but judging the current set up of the air vents I don't see that really happening. For the moment it is a mystery to me, but one thing I do know is that the ER is pretty hot.

OldDan1943 · Jun 22, 2022

I have my water maker in the ER and I am told, the the high temps in the ER will have a definite effect on the output.
Consider adding a couple of 12vt compartment fans to maybe stir up the ER air and lower the temp??

Mambo42 · Jun 22, 2022

Mako said:
Mambo, my buddy had a Mainship 34 with twin Lehman naturals. Always running hot. So I helped him to install two small bilge blowers, stuck up inside by the opening. We then ducted the blowers directly to the intakes of the engines. It dramatically lowered the op temperature down to normal levels. Focus on fresh air intake versus hot air exhaust

@ Mako

Great solution. If I may ask: 'where did you get the outside air from ?' Did you have to cut a new opening to the engine room or were there already opening pre arranged ?
My ER is below the salon and is basically an airtight space. To the front is a bulkhead and to the rear is a bulk head with an opening to the lazarette. The lazarette however also does not have any openings, other than a hatch. So in May we were running the boat the whole time with the door from the ER to the lazarette open as well as with an open hatch to the lazarette. Bit dangerous to have an open hole like that, but could not think of any other quick solution to bring cool air into the engine room. We ran the boat one day with door and hatch closed, it became a complete sauna after running the engines for 2 hours.

I think I will have to focus on the aft air vents and see if I can draw more air in via those vents. Or to have one vent draw the air and use the other as an exhaust.

Mambo42 · Jun 22, 2022

OldDan1943 said:
I have my water maker in the ER and I am told, the the high temps in the ER will have a definite effect on the output.
Consider adding a couple of 12vt compartment fans to maybe stir up the ER air and lower the temp??

@ OldDan,

Thanks for your thoughts on this one.

I agree I need something to stir up the ER air, but am thinking I also need some movement of fresh air into the ER and hot air out.

Getting the fresh air in I think I can find a way to do that, but I have no clue where the hot air should go.

Am even thinking to open up a hole through the bulk head to the master stateroom (I know, bad idea) so that I suck in the air from the master stateroom into the engine room, through the engine room and then out via the aft vents on the side deck.

The master stateroom will then also get ventilation since that will start sucking in air via the portholes or via the stairs to the pilot house.

Weird idea, but perhaps it works.

Mac2 · Jun 22, 2022

I am doing a similar project now. I have the benefit of a sister ship with a working cooling system to copy. My engine room has vents on each side of the boat . They are port and starboard at a height just above each engine and centered on each engine. My sister ship has two blowers attached to the starboard vent. They are controlled with a thermostat switch. When they kick on, they force air out of the engine room, which in turn, pulls air in from the port vent. On another boat I owned, I installed a blower to draw from the outside air and direct it towards the intake of the engine. This worked well. IMO if your forcing cool outside air in, the hot air has to go somewhere-hopefully out another vent, no matter where it's located.

Simi 60 · Jun 22, 2022

Ours has 4 inch PVC tubes X 6 inside ventilated lockers coming from 2 ft above front deck level down into front of the ER.

Hot air is vented at back of ER by big Davies Craig 24v radiator fans X 2 into ducting, up through a passageway through all levels and out through the rooftop funnel

Actual air the engine breathes comes from front of rooftop funnel, down into a box with a K&N filter and to the engine.

Have never seen more than 37c / 98f after long mid summer runs.

I do leave the ER door open, it's at front of boat in the forepeak, engine noise is minimal when underway.

Lepke · Jun 22, 2022

OldDan1943 said:
I have my water maker in the ER and I am told, the the high temps in the ER will have a definite effect on the output.
/QUOTE]

Membrane product flows are rated at 77°F. Higher water temp more product, lower temp - less. The maximum operating temperature at which my membranes can be operated is 113°. Above 113° the membranes degrade. Membranes need to be kept wet, so even if you're not making water in high temps, the water could be evaporating away from the membrane.

I run in cool climates and cold waters so use a inline heater to bring the water close to 77°.

Flatswing · Jun 22, 2022

My 49 RPH has air intakes via the PT& STBD steps from salon level (aft) deck to PH deck level. They open into ER just aft of forward bulkhead, above the stabilizers. There are additional vents from the aft side decks adjacent to the fuel tank vents. Both my JD 225 HP (&generator) use ER air with no ductwork and create a significant in draft through all 4 of these sources. Still, ER temps and battery temps routinely 100-105 deg. F underway at cruising speeds so my alternator often gets hot enough to decrease output and my Sterling Alternator to battery charger, hits the high temp limit, most summer days, after an hour or two of running. Batteries are in the ER, inverter is in the lazarette. 3 AC compressors add significant heat too if running. Running the blowers while cruising doesn’t change ER temps significantly but does help after we anchor along with opening aft ER door & lazarette hatch.

Would it be worthwhile in your situation, to temporarily disconnect the dedicated engine intake ducts, see if that entrains more outside air, and cooler temps?

I have 2 Jabsco 250 cfm blowers. PT: draws air in from intakes near tank vents, blows across front of engines. STBD blower exhaust air over aft fuel tank to STBD intakes. Blowers shut down spontaneously once the bearings start to go, just hard to hear the squeal over the engine noise

Mambo42 · Jun 23, 2022

Mac2 said:
I am doing a similar project now. I have the benefit of a sister ship with a working cooling system to copy. My engine room has vents on each side of the boat . They are port and starboard at a height just above each engine and centered on each engine. My sister ship has two blowers attached to the starboard vent. They are controlled with a thermostat switch. When they kick on, they force air out of the engine room, which in turn, pulls air in from the port vent. On another boat I owned, I installed a blower to draw from the outside air and direct it towards the intake of the engine. This worked well. IMO if your forcing cool outside air in, the hot air has to go somewhere-hopefully out another vent, no matter where it's located.

@ Mac2

Like your solution a lot. I do have the vents, so could adjust the blowers to draw from one side and have it blow out via the other vent. I will leave the vents for the engine as they are, otherwise I may open up another can of worms.

But great to hear you can copy from an existing boat where the cooling does work.

Mambo42 · Jun 23, 2022

Flatswing said:
My 49 RPH has air intakes via the PT& STBD steps from salon level (aft) deck to PH deck level. They open into ER just aft of forward bulkhead, above the stabilizers. There are additional vents from the aft side decks adjacent to the fuel tank vents. Both my JD 225 HP (&generator) use ER air with no ductwork and create a significant in draft through all 4 of these sources. Still, ER temps and battery temps routinely 100-105 deg. F underway at cruising speeds so my alternator often gets hot enough to decrease output and my Sterling Alternator to battery charger, hits the high temp limit, most summer days, after an hour or two of running. Batteries are in the ER, inverter is in the lazarette. 3 AC compressors add significant heat too if running. Running the blowers while cruising doesn’t change ER temps significantly but does help after we anchor along with opening aft ER door & lazarette hatch.

Would it be worthwhile in your situation, to temporarily disconnect the dedicated engine intake ducts, see if that entrains more outside air, and cooler temps?

I have 2 Jabsco 250 cfm blowers. PT: draws air in from intakes near tank vents, blows across front of engines. STBD blower exhaust air over aft fuel tank to STBD intakes. Blowers shut down spontaneously once the bearings start to go, just hard to hear the squeal over the engine noise

@ Flatswing,

Thanks for the input, nice to hear from someone who also has a Devefer 49 and as I understand you have the same issue. I have not had an overheating alternator, but am guessing I will get to that point in August. OAT will be about 50 to 60 degrees higher than what I encountered in May. Coupled with the much warmer water temperature I will be in for a treat.

But understand you disconnected the dedicated air intakes for the engines ?

Am a bit weary to copy that idea. Understanding that your blowers, in the current set up, don't really make a big difference in ER temperatures, I am leaning more to copying the idea of Mac2. Connecting to blowers to one vent and simply blowing it with force over the engines, perhaps even installing some air hoses (like you see in big shops) to disperse the air evenly and let it subsequently escape via the other aft vent.

I read you have actually 500 cfm total, which is much more than I initially had in mind, so need to upgrade to your level at least.

You state that you have 3 airco's running. Are they air cooled or water cooled ? If they are air cooled, then indeed they do add more heat to the ER. I have 3 water cooled airco's, have no problem with them generating heat. Only problem could be that the cooling water is a bit too warm, resulting in less cooling capacity, but I guess I will also find that out in August.

The opening of the hatch of the lazarette is something I am indeed also familiar with and it does indeed help. Only is a bit of a problem if that is exactly the area where you want to sit or where you constantly need to pass by when you go for a swim. On top of that, we have 4 dogs on board and 2 of them already fell in the lazarette while in port, so I need to find a solution where I can keep the hatch on.

But again, thanks for your input.

klee wyck · Jun 23, 2022

I think a 200 hp engine is itself a 500 cfm blower. If the exhaust path is cool and the engine intake vents are at the furthest point from the engine air intake, then the engine itself should ventilate the room pretty decent taking cool air in and exhausting the hot air outside the boat.
My engine rooms only get truly uncomfortable after I shut the main down on a hot day.
The main does run pretty cool though at around 78 C under load.

Mambo42 · Jun 23, 2022

Simi 60 said:
Ours has 4 inch PVC tubes X 6 inside ventilated lockers coming from 2 ft above front deck level down into front of the ER.

Hot air is vented at back of ER by big Davies Craig 24v radiator fans X 2 into ducting, up through a passageway through all levels and out through the rooftop funnel

Actual air the engine breathes comes from front of rooftop funnel, down into a box with a K&N filter and to the engine.

Have never seen more than 37c / 98f after long mid summer runs.

I do leave the ER door open, it's at front of boat in the forepeak, engine noise is minimal when underway.

@ Simi

I wish I could install that kind of cooling pipes, that surely does work.

Unfortunately there is no way for me to get a 4" pipe into the ER without cutting holes in either the salon or the master cabin. In itself I have no problem cutting into the master cabin, but I must be sure it will be an improvement, otherwise am not going to gamble.

Any case thanks for your insight.

Engine room heat

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