Engine Room Temperatures

[firehoser75]

I am looking for advice and preferably experiences from those who have installed fans/blowers in the engine room to reduce ER temperatures.
Some background. I have read that engine room temperatures should never exceed 115 degrees F (mine have not) and that optimally the differential between the outside temperature and the ER temperature should not exceed 30 degrees F. So for example, if the outside temp is 68 degrees F and the ER temp is 105 degrees F, in theory your ER is too warm??
Also, having a cooler ER would benefit any installed items located there, for example battery chargers, inverters, batteries, solar controller, and even the engine alternator, etc.
My engine room temperature often exceeds the 30 degree differential and I am hoping to find a way to "cool" the ER without having to conduct major surgery like adding more holes, etc. Not going there!

I am thinking about adding a blower (maybe even 2), but don't want to go to the expense and trouble if it will not be effective. I am hoping for a reduction in temp of about 10 degrees F.
If I add blowers, my goal would be to exhaust at least as much air as I may increase intake (don't want to pressurize the ER possibly forcing gases and heat into the boat).
Has anyone had experience with this with good results? If so, what brand/model of blower and where in the ER did you locate it (them).
I have not experienced any operating problems associated with this higher than optimal temp difference, but I can understand the potential benefits (overall) of having a cooler ER.
Thanks,
Tom

 

[Comodave]

If you add exhaust blowers then you will probably have to add intake vents or you may starve your engine(s) of combustion air. Have you looked at Delta blowers? Good but pricey.

 

[Ski in NC]

It is difficult to cool an ER much unless you use really powerful fans. Pretty much anything in there can tolerate the higher temps seen without any added ventilation. The engines draw in a fair amount of air and that helps things stay cooler. More so with bigger engines at high power.

I would not bother. Let it find its natural temp. Batts are low and have a lot of thermal inertia, they should stay pretty cool. Inverter should be designed for warm environments and be ok too. Check the manual. Anything critical on engine is water cooled.

The only time I run engine room ventilation is on a hot day with gennie on and main engine off. Since genny end is air cooled, it can get pretty dang hot.

 

[Alaskan Sea-Duction]

I am looking for advice and preferably experiences from those who have installed fans/blowers in the engine room to reduce ER temperatures.
Some background. I have read that engine room temperatures should never exceed 115 degrees F (mine have not) and that optimally the differential between the outside temperature and the ER temperature should not exceed 30 degrees F. So for example, if the outside temp is 68 degrees F and the ER temp is 105 degrees F, in theory your ER is too warm??
Also, having a cooler ER would benefit any installed items located there, for example battery chargers, inverters, batteries, solar controller, and even the engine alternator, etc.
My engine room temperature often exceeds the 30 degree differential and I am hoping to find a way to "cool" the ER without having to conduct major surgery like adding more holes, etc. Not going there!

I am thinking about adding a blower (maybe even 2), but don't want to go to the expense and trouble if it will not be effective. I am hoping for a reduction in temp of about 10 degrees F.
If I add blowers, my goal would be to exhaust at least as much air as I may increase intake (don't want to pressurize the ER possibly forcing gases and heat into the boat).
Has anyone had experience with this with good results? If so, what brand/model of blower and where in the ER did you locate it (them).
I have not experienced any operating problems associated with this higher than optimal temp difference, but I can understand the potential benefits (overall) of having a cooler ER.
Thanks,
Tom

Hey Tom, question. Your ER does not have blowers? Gas or Diesel?

 

[kchace]

MY ER usually runs about 100-105F when cruising on a warm sunny summer day. One day I tried running the main blower (250CFM) while cruising. Running it continuously for several hours while cruising the temp was about 1 degree cooler.


Ken

 

[Martin J]

I did fit fans intake & exhaust to my last boat (Cheoy Lee 50) after seeing 130 F temps and above. I bought 550cfm Spaal exhaust fans from the surplus center. and mounted them aft in the engine room above the risers. The intakes @500cfm were ducted to blast the cooler ambient air from outside directly to the vicinity of the engine intakes. This with natural unforced air through other areas reduced my engine room temps down by 20 degrees. The fuel economy improved as did the engine performance. Engines run smoother and perform better with cooler denser intake air. My service batteries some 10 trojans seemed to also perform better. There are also benefits to the rubber products etc in longjevity of these items (belts/hoses etc. Currently doing the same to the new boat Cheoy Lee 67. Caterpillar Have a publication showing large amounts of info on this subject. It's available on Line.

 

[Martin J]

There is also a thread somewhere on this subject I started a few years ago.

HP Power Loss due to high E.R. temp

http://www.trawlerforum.com/forums/s6/hp-power-loss-due-high-e-r-temp-21548.html

 

[gsholz]

I view the 30 deg max difference as more of a design target. The absolute temp is what counts in the end.
To see if a blower would make a significant difference you can estimate how much air your engines are moving. For naturally aspirated 4 stroke engines it would be displacement in liters times half the cruise RPM times 60. This yields air consumption in liters per hour. 2 stroke engines would require 2x the air and turbo engines would require significantly more.

You’ll find the engines are pretty good air pumps when running. Most blowers are just used to evacuate fumes or cool down the engine room after shutdown to allow repairs etc

 

[dhays]

I view the 30 deg max difference as more of a design target. The absolute temp is what counts in the end.

To see if a blower would make a significant difference you can estimate how much air your engines are moving. For naturally aspirated 4 stroke engines it would be displacement in liters times half the cruise RPM times 60. This yields air consumption in liters per hour. 2 stroke engines would require 2x the air and turbo engines would require significantly more.



You’ll find the engines are pretty good air pumps when running. Most blowers are just used to evacuate fumes or cool down the engine room after shutdown to allow repairs etc

That is my thought. I will often turn on the engine blower as I idle to my home dock. About 20 minutes of idling. Not sure if it helps a lot but then I leave the blower on while I connect the fresh water flush and flush the engine and then the genset. The blower on after shut down makes the ER much cooler to work in.

I don’t think it would make much different at all when the engine is running at our normal cruise RPM.

 

[ben2go]

How is your exhaust insulation holding up? If you have turbos, do they have insulating covers? Maybe cutting down on some heat output along with adding some air movement will help.

 

[BruceK]

Run the mains for several hours, exhaust blower on, ER will be warm. Same scenario minus the blower, it`s seriously hot, only happens if I forget to activate the blower.
Another plus of my exhaust blower, it`s right above the compressor for the eutectic fridge and the freezer, activated, it shortens compressor run time.
I have good venting for intake, and the blower has a dedicated vent.

 

[firehoser75]

Hey Tom, question. Your ER does not have blowers? Gas or Diesel?

No blowers. Single Diesel.
The turbo does not have insulation, but the exhaust insulation is in excellent condition (only 2 years old).

This summer, I experimented a bit. I ran a small (8-10 inch)12v fan for a while just moving air around a bit, but pointed towards one of the ER vent openings. Just using this (while underway), I often lowered ER temperature by as much as 3-4 degrees F.

By the way, I usually cruise at about 1/2 throttle on my Cummins 6BTA 5.9L engine, so the turbo is normally not involved much (if at all). Normal ER temps seem to average 102 to 107 F when there are light winds, and if the wind is up (10K or above) the temps are usually a bit lower (98 - 102).
The engine cooling system is well maintained and does not run hot at all. I check fairly regularly with an IR thermometer. I am monitoring ER temps with a remote sensor from a "home type" weather station. The sensor is sitting on top of the generator (gen not running when underway) about 2.5 feet below the ceiling of the ER.
What I was hoping for, was an ER temp below 100 F even when there are light winds.
Maybe another year of experimenting?? Being as I run the inverter when underway to power the laptop, etc. maybe I should try using a 120v larger fan in the ER (similar to what I did with the 12v this year a few times) and see what that does? It might give me an idea of how effective (or not) adding a blower would be.
Martin J. I agree that cooler ER temps are better than hotter ER temps for a number of reasons.
Thanks for all your thoughts,
Tom

 

[Snapdragon III]

My boat came with a beefy engine room ventilation system that works like a charm. It has about an 18"x18" intake that chases down to a large 12v radiator fan that is bolted to the wall of the engine room. There is a second chase at the top of the engine room that the dry exhaust runs through that allows the hot air to rise up and exit a large louvered grate in the back of the stack above the pilot house. Due to the stack, and the exhaust being on the back of the stack with slightly lower air pressure, convection makes it flow quite a bit even when the fan isn't on. The fan is wired to a thermostat. I usually set it at 90 degrees, and the fan seems to run about 1/4-1/2 the time depending on how hot it is outside. if you add an intake and exhaust I would put the intake near the floor, and the exhaust near the ceiling. I would go for it, it is better for the gear, and makes things much better if you have to go down there and work on something.

 

[O C Diver]

When I bought my boat it had a single Cummins 6CTA 450 HP engine and 4 blowers of the 220 cfm variety with 2 blowing in and 2 blowing out. During my refit, I swapped to a Deere 4045TFM75 135 HP engine. Thoroughly examined the blower systems, crushed dryer hose they were hooked to, and the convoluted venting in the sides of the boat. Did some extensive research on engine room ventilation and air flow. Ended up building a pretty cool system for way to much money that keeps the inside outside differential below 25 degrees, with one 220 CFM blower!

First, where do you measure the temperature? The difference between inches off the floor and just below the ceiling can be 25 degrees or more. My digital thermometer probe is 2" below the ceiling.

If you're going to install an exhaust fan, it should also be just below the ceiling (hot air rises, and you want to exhaust the hottest air). If you're going to blow in cooler air, it should be directed to the lowest point. The object isn't to mix the air. The object is to exhaust the hottest from the top and have the cooler air replace it from the bottom. Ideally, the hot air should be evacuated from one end of the engine room and the fresh air should enter from the opposite end. All of this should seem basic and logical. Sadly most manufacturers seem to ignore the basics when it comes to venting the engine room.

Should you blow air in? It's important to have enough air for the engine(s), generator, and ventilation. If you can't supply it through enough square inches of supply vents, then a blower may be needed. IMO, that should be the last resort. The only real down sides to pressurizing the engine room is smells and possibly exhaust leaks will find their way into the living spaces within the boat, and if an intake blower fails, you may starve the engines of fresh air. So, provide enough intake air and only use blowers to exhaust gas.

A brief overview of the basic 220 CFM engine room blower:
These blowers are designed to move large volumes of air with very low static pressure and minimal vacuum. Obviously you need a free flowing volume of air for the blower as they can only create minimal vacuum. Of equal importance is the discharge resistance. Several things contribute to the loss of some to most of the CFM output. First is frictional line loss. This occurs as the air is pushed through a tube that is the same diameter as the fan. The air is moving, but the tube walls are stationary, creating a resistance to the air flow. Make the tube long enough and no air will flow through because of the resistance. Next are bends in the tube. A 90 degree bend has a significant impact on air flow. Don't quote me on this, but each 90 I believe is worth 10' of frictional line loss. Next are hoses or tubes with internal ridges (like dryer hose) which disturb the air flow (smooth tube or hose is much better). To summarize, a tube larger than the diameter of the fan, of a smooth bore, with the shortest distance, and the least amount of sweeping bends, will yield the highest airflow from the standard blower.

So, with this information, I set out to build the optimal engine room ventilation system. The supply air utilized 2 existing vents and I added two super vents (pictures at the end). The new vents enter under the winch platform, drop through the deck into the chain locker, exit into the large hollow keel, and travel back to the engine room. By entering the room through the keel, the cooler fresh air is entering at the lowest point. There is a water trap below the winch pedestal, one in the chain locker, and one before entering the engine room. In addition to supplying plenty of fresh air, the flow going through the chain locker and bilge keeps those areas dry and fresh (not musty).

For the exhaust blower I took a standard 4" blower and adapted it to 5" smooth bore fiberglass exhaust pipe (told you this was expensive). To understand the logic for 5" pipe, you need to calculate the cross sectional area of each pipe. 4" pipe has an area of 12.5". 5" pipe has an area of 19.5. With greater than 50% more area, the 5" pipe has a much lower frictional line loss. In essence, more of the air flows through the center of the pipe faster, and less is slowed down by contact with the wall. The pipe exits the engine room in the stern near the ceiling, under the back deck, around a water block loop, and exits the transom under the swim platform. The water block loop is 16" above the back deck and maybe 30" above sea level. All the 90s are sweep, smooth bore, rubber exhaust elbows (double T bolt clamped on each end ).





So how well does all this over engineering work? When you turn the blower on with the engine running full RPM (in neutral, tied to the dock) the airflow from the blower, ripples the water out past the swim platform. I run the blower whenever the engine or generator is running. The blower typically lasts 1,500 hours. I think they're about $30 or $40 dollars which I consider a small price to pay for a cool engine room.

While it's unlikely that anyone without OCD would go to this effort and expense, I hope that those analyzing their engine room ventilation, can use some of the above information to improve their ventilation.

Ted

 

[firehoser75]

Thanks Ted for the great, detailed (time consuming for you) response. I learned alot, and got some good ideas, although, I don't have plans to go as far as you did
I particularly liked your real world data on how long you have found that the inexpensive fans seem to last! I was looking at much more expensive models, but maybe the less expensive ones make more sense, cause in a way, I would be going with a more "hit or miss" approach.
Thanks to everyone else for your contributions, I appreciate all of the advice, opinions, and real world experiences described.

Ted, are those fans you described by any chance "reversible" as to direction of flow?
Just thinking...... as my ER vents are on the side of the hull it might be good to be able to reverse the flow so as not to "fight" the natural ventilation when the wind is coming more one side than the other???? Maybe I am overthinking this?
Thanks again,
Tom
PS: Just curious Ted, why the switch to the smaller engine? Did fuel economy improve alot? Boat performance improve?

 

[O C Diver]

Ted, are those fans you described by any chance "reversible" as to direction of flow?
Just thinking...... as my ER vents are on the side of the hull it might be good to be able to reverse the flow so as not to "fight" the natural ventilation when the wind is coming more one side than the other???? Maybe I am overthinking this?
Thanks again,
Tom
PS: Just curious Ted, why the switch to the smaller engine? Did fuel economy improve alot? Boat performance improve?

Don't know if the blowers are reversible, but if it's having a hard time exhausting against the wind, it's probably time to seek safe harbor.

Regarding switching to a smaller engine for better fuel economy, here is a post I wrote on the subject:

New Engine Economy Numbers

It's from this thread on my refit project

My Short Haul Refit

All in with the new prop I have about $12K invested. The numbers worked for me, but most people would have 3 times as much invested and wouldn't cruise enough to begin to recover the money. With the current price of fuel, My break even between repower cost and fuel cost savings is about 3,000 hours (which I will reach next summer). For most, it could be 9,000 hours.

Ted

 

[FF]

Has a wave ever climbed aboard flooding the air intakes offshore?


Do you have storm covers?

 

[O C Diver]

Has a wave ever climbed aboard flooding the air intakes offshore?


Do you have storm covers?

No, the forward deck is over 5' above sea level and the front of the bulwarks are around 8' above sea level. The forward deck also has substantial scuppers. Been bow into 7' seas without anything but spray coming over the bulwarks. There is a water block in the form of a square fiberglass and coosa board tube that is fiberglassed to the deck and goes up about 12" behindthe front vents. The area below the tube is the chain locker which has 3' high walls, and an overboard discharge pump with float switch. Boat is a coastal cruiser and have no intention of seeing 7' seas again.



Ted

 

[rslifkin]

Has a wave ever climbed aboard flooding the air intakes offshore?

Do you have storm covers?

That can be a concern. I've taken water (although not very much) down an engine room vent only once that I know of. The bigger concern was that it damaged the stainless steel vent which had to be replaced.

I think with decently designed vent boxes and a bilge drainage and pump layout that can easily handle a little water at the vent locations, it would take fairly bad conditions to get enough water down there to be a problem.

 

[garycasey]

Cooling the ER

I am looking for advice and preferably experiences from those who have installed fans/blowers in the engine room to reduce ER temperatures.
Some background. I have read that engine room temperatures should never exceed 115 degrees F (mine have not) and that optimally the differential between the outside temperature and the ER temperature should not exceed 30 degrees F. So for example, if the outside temp is 68 degrees F and the ER temp is 105 degrees F, in theory your ER is too warm??
Also, having a cooler ER would benefit any installed items located there, for example battery chargers, inverters, batteries, solar controller, and even the engine alternator, etc.
My engine room temperature often exceeds the 30 degree differential and I am hoping to find a way to "cool" the ER without having to conduct major surgery like adding more holes, etc. Not going there!


Has anyone had experience with this with good results? If so, what brand/model of blower and where in the ER did you locate it (them).
I have not experienced any operating problems associated with this higher than optimal temp difference, but I can understand the potential benefits (overall) of having a cooler ER.
Thanks,
Tom

AS with the comments from Tom above, I, too was "concerned" about ER temperatures, so I put a thermocouple in the ER, located directly above the engine, probably the hottest location. I found that the temperature on a warm day of about 80 degrees was about 125. I considered that reasonable, so I pulled the thermocouple out and quit worrying. I'm sure the temperature varies widely depending on wind speed and direction.
So what is bad about higher engine room temperatures? Yes, the maximum power of the engine is pretty much inversely proportional to absolute temperature of the inlet air. A 5-degree(F) drop will produce about 1% more power. However, that is only when running at full power. With a diesel running at partial power (how much time do trawler operators run at full power? I would guess essentially zero) HIGHER inlet air temperature is a benefit in that it reduces ignition delay and therefore combustion noise. Engine efficiency also increases.
Does a "high" ER temperature decrease the life of rubber components? I doubt at any temperature below 200 there is a measurable difference. Does it increase the amount of heat conducted into the cabin? Certainly, but the temperature, at least in my Nordic Tug, is barely noticeable.
One responder noted that he had an air-cooled generator mounted in the ER. That is a totally different situation and I would recommend adding a sealed duct to direct the cooling discharge air to the outside.
The only complaints from my crew is that the "cold" water isn't cold. Yes, eventually the water supply system in the ER gets warmed up. I've thought about moving that out of the ER, but that's a lot of work.
So my recommendation is to simply not to worry about it.

 

[Ski in NC]

Yep, I would not worry about trying to keep it cool down there.

To clarify, the genny has a water cooled engine, but the electrical end is air cooled (most are like this). Really need some air moving on hot days or it does build up. It felt much worse down there in the summer with gen on/main off than with main on/gen off. Mostly due to the main sucking in a good bit of air.

And true, unless at full power the higher intake air temp will have no ill effect on the diesel. Full power is a different story, but who runs there.

My water tank is in the ER too. In the summer that tank can soak up some decent heat if run more than a day. Can get a little annoying. No need to run the water heater much though for a good shower!

 

[twistedtree]

ER temp definitely matters. The predominant limit from equipment manufacturers is 130F, and some are lower i.e. Detroit/MTU Series 60 which call for something in the 115-120F range. Heat impacts seal life, electronics including those that are part of the engine, plus gear/throttle controls, battery chargers, inverters, fans, etc. Things won't fail immediately if you exceed 130F, but you will see shortened life on components.


The other consideration is you, if you need to spend any appreciable time in the ER fixing something. Above 120F is down right hazardous to your health, not to mention darned uncomfortable.


Keeping an ER cool is all about air flow through the space. Cool air is drawn in, gets heated by the hot equipment, and exits somewhere carrying away that heat. There is no substitution for air flow. Sometimes is can happen "naturally" with large vents plus the air flow through the engine itself, which is significant. My previous Grand Banks worked fine this way, mostly because of the very large vents on both sides of the ER.


Big vents work fine for boats operating in moderate conditions, but those same vents pose unacceptable down flooding exposure in sea-going boats, so their vents tend to be sized only as large as necessary, and located higher up with connecting ducts. In these circumstances mechanical ventilation is almost always needed for acceptable ER temps.


I dug into all this pretty deeply on our last Nordhavn and wrote a couple of bog articles that can be found starting here Adventures of Tanglewood: Engine Room Cooling
If you search on "ventilation" on the blog there are a few other related articles that might be helpful.

 

[O C Diver]

AS with the comments from Tom above, I, too was "concerned" about ER temperatures, so I put a thermocouple in the ER, located directly above the engine, probably the hottest location. I found that the temperature on a warm day of about 80 degrees was about 125. I considered that reasonable, so I pulled the thermocouple out and quit worrying. I'm sure the temperature varies widely depending on wind speed and direction.
So what is bad about higher engine room temperatures? Yes, the maximum power of the engine is pretty much inversely proportional to absolute temperature of the inlet air. A 5-degree(F) drop will produce about 1% more power. However, that is only when running at full power. With a diesel running at partial power (how much time do trawler operators run at full power? I would guess essentially zero) HIGHER inlet air temperature is a benefit in that it reduces ignition delay and therefore combustion noise. Engine efficiency also increases.
Does a "high" ER temperature decrease the life of rubber components? I doubt at any temperature below 200 there is a measurable difference. Does it increase the amount of heat conducted into the cabin? Certainly, but the temperature, at least in my Nordic Tug, is barely noticeable.
One responder noted that he had an air-cooled generator mounted in the ER. That is a totally different situation and I would recommend adding a sealed duct to direct the cooling discharge air to the outside.
The only complaints from my crew is that the "cold" water isn't cold. Yes, eventually the water supply system in the ER gets warmed up. I've thought about moving that out of the ER, but that's a lot of work.
So my recommendation is to simply not to worry about it.

I suppose if you never cruise your boat South, a 45 degree differential might not be a problem. However, if you see outside temperatures between 90 and 100 degrees, you might want to rethink that.

Ted

 

[Ski in NC]

On larger vessels, ER ventilation does become a big deal. On small vessels, there are not many sources of heat and proportionately more ways for heat to transfer out of the engine room.

Get a large engine room with large (and more) machines and the math is different. And also the expectation that the ER be habitable. It can get too hot, something needs to be done.

On mine, the inverter and charger are not in the ER, so no worries there.

I don't worry about things like hoses and other engine bits. Same material is used in car/truck engine compartments. Hold up fine when a car is parked after running with 200F coolant and AC on and then machine shut down in full sunshine. That engine compartment is way hotter than any of our boat ERs, and has basically the same equipment.

Would I like better forced ventilation in my ER? Sometimes, especially if I have to go down there for any length of time after a run. Is it worth it to improve it? To me, no.

I have had zero heat related failures in the ER in 12yrs and 2700hrs run time, so there is that.

 

[Crazymonkey]

We have blowers in our engine room but dont really use them....we have a rotating fan in the engine room that we run all the time....just keeps the air moving all the time. We have a trawler with twin diesels. Never had a problem

 

[firehoser75]

Thanks everyone for your thoughts on this subject!
While I understand and somewhat agree with the posters who say: " leave it alone", and I illustrate this idea with the fact that I am not willing to undergo "major surgery" such as enlarging the ER side vents, I am hoping (maybe naively) that by adding a couple of fans, one up high in the ER and ducted to help draw more air in towards the engine air intake, and one on the other side of the ER up high to "push" air outside through the existing vents, I might be able to reduce average ER temperatures by 10 degrees F.
This summer, I did see a small drop in ER temperatures when I ran a small (7 inch) fan in the ER just pointed up out one of the ER vents (a drop of 3-4 degrees). That experiment is what got me thinking about all of this. I am thinking (maybe incorrectly) that most boaters don't really know what their ER temperatures are or what they really should be???

Thanks again for the interesting discussion,
Tom

 

[twistedtree]

I think your assessment is correct. Most boaters simply ignore it, assuming all is fine. And few builders have really engineered a good cooling system. Most get by because failures are sparse enough to not be attributable to ER temps. My Northern Lights contacts say engine oil seals suffer from high temps, and guess what people with high ER temps end up replacing? But the cause and effect is lost over the years.

The manufacturer limits are clear and consistent: 130f max temp, and 30F Max delta over outside ambient. More than that will fail sea trial by pretty much every manufacturer, and void warranty. There is a reason for that.

What it takes to meet the specs varies widely from boat to boat, but meeting it does matter.

 

[Simi 60]

We have 6 x 4 inch PVC pipes a foot off the front deck, enclosed in a vented locker running down to knee height in the front of the ER.

At the back of the ER we have 2 x 16inch Davies Craig 24v fans sucking hot air out and through the funnel on the roof.

Clean air for the engine comes in from the funnel on the roof to a sealed box with air cleaner on the ER ceiling then into engine.

Never seen temps in their over 100f 38c in sub tropical summer.

 

[Simi 60]

What are thoughts on leaving ER door open?
As we plan on heading up to equatorial waters next year I reckon heat may be more of an issue.

 

[Delfin]

I am looking for advice and preferably experiences from those who have installed fans/blowers in the engine room to reduce ER temperatures.
Some background. I have read that engine room temperatures should never exceed 115 degrees F (mine have not) and that optimally the differential between the outside temperature and the ER temperature should not exceed 30 degrees F. So for example, if the outside temp is 68 degrees F and the ER temp is 105 degrees F, in theory your ER is too warm??
Also, having a cooler ER would benefit any installed items located there, for example battery chargers, inverters, batteries, solar controller, and even the engine alternator, etc.
My engine room temperature often exceeds the 30 degree differential and I am hoping to find a way to "cool" the ER without having to conduct major surgery like adding more holes, etc. Not going there!

I am thinking about adding a blower (maybe even 2), but don't want to go to the expense and trouble if it will not be effective. I am hoping for a reduction in temp of about 10 degrees F.
If I add blowers, my goal would be to exhaust at least as much air as I may increase intake (don't want to pressurize the ER possibly forcing gases and heat into the boat).
Has anyone had experience with this with good results? If so, what brand/model of blower and where in the ER did you locate it (them).
I have not experienced any operating problems associated with this higher than optimal temp difference, but I can understand the potential benefits (overall) of having a cooler ER.
Thanks,
Tom

If you can supply cool air to the engine air intake, the background temp of the ER is irrelevant unless you're cooking your batteries or alternator. I installed a 10" axial blower to discharge more or less in the direction of the CAT air intake and divert some cooling air to the battery compartment. With that setup, I could care less what the ambient temp in the ER is.