Comprehending the air cavity for engine air cooling as it's very confusing help...

[LeifThor]

1972 Ericson 35-2.
Atomic 4 engine under seatee in lounge area.

Blower (working great) sucks air from bilge area under engine, opening is 4-5 inches from transmission box, exits out starboard stern side through cowling.
Cowling providing air intake on port stern side (so a flow of air in air out around the engine) 3 inch blower hose end at front top of engine on the left side.

SOOOO, in theory there should be a nice circulation of air running from the top of the engine compartment over the engine, and then getting sucked out the other end of the engine just underneath so the air is being replaced with outside cool air to help cool the engine roughly every 30 seconds.

Then the more I thought about it, I realized in totality there's a huge air cavity from which the air getting sucked out, so it could simply use that air bypassing the cowling vent providing replacement air, meaning you think the engine is getting cooled, but it's not, instead it's sucking the air from behind the cabinet behind the stairs.

I tried running the blower using incense on the intake side and there was 0 suck, no smoke going in.

I realized there were more than a few air holes to help in ventilation (top of cabinet behind stairs, side of rear quarter berth bed, and in my particular case gaps between the wood housing around the engine (part of the seatee) and the fiberglass sole of the boat which comes up 5 inches from the floor.

I plugged every one of them, and still zero suck from the air intake side.

In theory, if there's a large hole to pull air in from, it would use that large hole, or if there's holes closer to the vacuum end it might draw the air from there.

What puzzles me, is the way the engine compartment is where there's no air containment, or the air in the engine compartment is also the same air cavity behind the cabinet behind the stairs, the large locker on the starboard side of the cockpit, the cabinet under the sink...If I were to fill the cavity with water it would be hundreds of gallons, instead of the 20 the engine compartment alone takes up.

This feels like bad design, and I hate to say that as I love my Ericson so much and find so much of it's design impeccable. But here, in short it's terrible as there's a far more likelihood the air will get sucked from everywhere but the engine compartment as it's a much easier place to get the replacement air from.

And there's no way I can see to fix this, or there's no way to partition off the engine area, so it's forced to suck the air from the outside vent/cowling on the port side so an airflow can exist to run over the engine so it can cool down.

I should add, when my atomic is running she cools beautifully! You can put your hand directly on the engine and it's luke warm. It's only when the engine is turned off, it becomes quite hot and hot in the engine compartment. It gets so hot, it's slightly melted the cushion on top (through the cracks between the engine cover the remainder of the seetee).

In the past, I've simply removed the cover so it can cool freely. Now I've got a new lounge single piece, so I need to address the blower cooling system.

Any ideas anyone?

 

[Christian Williams]

The primary reason for a blower with a gasoline engine is to expel fumes before starting it. Let the blower run for at least five minutes.

If your blower isn't up to your standards, there are bigger blowers/exhaust fans on the market.

But I think the threat is an accidental pool of gasoline in the bilge the cloud of vapor to be set off by the ignition switch. That is, a catastrophic scenario. For what it's worth, typical blowers in sailboats never impressed me with any great output. My current boat had three in-line blowers in a sea of vent hoses and the output was really insignificant--the corrugated, twisty hoses killed the flow. (I tossed them all in favor of passive venting, which is OK with a diesel).

 

[goldenstate]

1972 Ericson 35-2.
Atomic 4 engine under seatee in lounge area.


Any ideas anyone?

I found that the blower vents in the engine bay for my 3 cylinder diesel don't do very much. The seawater being pumped through your engine's heat exchanger is what keeps the block cool. I was concerned about the ambient temperature for my voltage regulator (electronics, battery charging) and so I bought an inexpensive wireless thermometer to keep in the engine bay:

https://www.amazon.com/AcuRite-00424CA-Digital-Thermometer-Temperature/dp/B00WXIR94M/ref=sr_1_5?crid=12WPDORO4GAPM&keywords=wireless+thermometer+indoor+outdoor&qid=1670628398&sprefix=wireless+thermometer+%2Caps%2C133&sr=8-5

It never got hot enough to worry about. So I don't.

Someone will say your blower must work to prevent carbon monoxide buildup, and to keep gas fumes moving out of your engine bay. Given the combustibility of gas, this is likely to be a valid concern.

 

[steven]

during (correct) operation why would there be gas fumes in the engine compartment (or anywhere except out the exhaust) ?

 

[LeifThor]

The primary reason for a blower with a gasoline engine is to expel fumes before starting it. Let the blower run for at least five minutes.

If your blower isn't up to your standards, there are bigger blowers/exhaust fans on the market.

But I think the threat is an accidental pool of gasoline in the bilge the cloud of vapor to be set off by the ignition switch. That is, a catastrophic scenario. For what it's worth, typical blowers in sailboats never impressed me with any great output. My current boat had three in-line blowers in a sea of vent hoses and the output was really insignificant--the corrugated, twisty hoses killed the flow. (I tossed them all in favor of passive venting, which is OK with a diesel).

I know the blower's primary function is to clear any gas fumes, and it does a fine job for that which is good news.

My issue, is because my engine is under the seatee, there's roughly 1 inch or less gap between the top of the engine, and the wood lid on top of the engine. For engines behind the stairway, they usually have 5-10 inches of space and more as there's more room for the hot air to rise. In my case I got nothing, it's a hotbox with no place for the hot engine (after it's off and not getting the water cooling) and engine area to cool.

Hmm, I wonder if I put in a few of the venting holes, or a grated piece at the other end of the engine it might pull air from the cabin area into the engine area, and out through the blower.

Another idea is with the bottleneck of the air cavity. I could get foam and cut out custom pieces to fill that in reducing the cavity it's drawing from.

I also realized looking at the air in side, there might be water that's filled the hose in a section, which has cut that hose from passing air entirely. I ran a fan blowing positive air through it from the engine side, and felt nothing on the cowling end, which implies either it's cut up badly, or there's water or some obstruction along it's 15 ft of length.

 

[Loren Beach]

I guess I am the "odd man out" here (surprise surprise) but our previous axial-flow blower put out a 130 CFM thru the vent located by the stern, aft part of cockpit. The current new one is a squirrel cage type rated at about 112 CFM. To me, both put out a major rush of *warm air from the vent. I changed to a different design because it is quieter. I would note that this is not the same as "quiet" which would be better yet...!

*Nice for warming a hand when motoring on a cold winter day.

Returning the OP's concern about air supply, usually on all boats there is plenty enough room for air to be drawn forward to the engine compartment in boats with a mid engine. (E-35-2, Catalina 30, Some later E-38-200 series, and many others)
With a gasoline aux. the intake for that exhaust air will be low down under the engine somewhere.; opposite of where it will be for a diesel.

 

[LeifThor]

during (correct) operation why would there be gas fumes in the engine compartment (or anywhere except out the exhaust) ?

Gasoline engines require a blower to remove any gas fumes which are explosive. Takes about 30 seconds to 1 minute. Not doing it can cause an explosion which along with having a gasoline tank and engine makes for a really bad day.

My issue is something else though. My engine compartment is contained, non venting, with a ceiling 1/2 from the top of the engine. So I need to come up with a solution after the engine is off. When it's running, my water cooling worked brilliantly, it's only for when it's off for 20 min after running. During that period it get's really really hot in the engine compartment.

 

[LeifThor]

I guess I am the "odd man out" here (surprise surprise) but our previous axial-flow blower put out a 130 CFM thru the vent located by the stern, aft part of cockpit. The current new one is a squirrel cage type rated at about 112 CFM. To me, both put out a rush of warm air from the vent. I changed to a different design because it is quieter. I would note that this is not the same as "quiet" which would be better yet...!

Hmmm, Loren, you just gave me an idea.
If I simply switch where the blower is to the other side, then the hose that's at the top of the engine compartment will suck, and have a higher likelihood of drawing the air from the engine compartment than working to draw the air from the bottom of the bilge which is attached to the huge air cavity that I've been wondering if I could close up. This would be the easiest and most effective solution so far.

 

[Kenneth K]

The thermostat should keep the engine at 180 to 190 degrees while running. Sounds like it is doing this. So, when you shut the engine down, it should be at ~190 degrees and not creating any additional heat. Not sure that the engine would be getting much hotter once you shut it down.

Less airflow once the boat stops moving, yes. More heat, likely no.

 

[Loren Beach]

then the hose that's at the top of the engine compartment will suck

I thought you said you have a gas engine. You need and want that blower intake to be able to suck up heavy gasoline fumes from the low point. That's very important. We do not want to lose any Vikings in a fiery explosion! Viking are legendarily tough... but they are not flame proof.

 

[LeifThor]

I guess I am the "odd man out" here (surprise surprise) but our previous axial-flow blower put out a 130 CFM thru the vent located by the stern, aft part of cockpit. The current new one is a squirrel cage type rated at about 112 CFM. To me, both put out a major rush of *warm air from the vent. I changed to a different design because it is quieter. I would note that this is not the same as "quiet" which would be better yet...!

*Nice for warming a hand when motoring on a cold winter day.

Returning the OP's concern about air supply, usually on all boats there is plenty enough room for air to be drawn forward to the engine compartment in boats with a mid engine. (E-35-2, Catalina 30, Some later E-38-200 series, and many others)
With a gasoline aux. the intake for that exhaust air will be low down under the engine somewhere.; opposite of where it will be for a diesel.

 

[LeifThor]

The thermostat should keep the engine at 180 to 190 degrees while running. Sounds like it is doing this. So, when you shut the engine down, it should be at ~190 degrees and not creating any additional heat. Not sure that the engine would be getting much hotter once you shut it down.

Turn on a space heater. Now cover it with a box that gives it 1 inch of clearance on all sides. While she runs she runs cool as a cucumber, can put my hand on the engine and it's luke warm. It's after it's off without the aid of the water cooling and it's confinement in a very tight space.

 

[LeifThor]

I thought you said you have a gas engine. You need and want that blower intake to be able to suck up heavy gasoline fumes from the low point. That's very important. We do not want to lose any Vikings in a fiery explosion! Viking are legendarily tough... but they are not flame proof.

Gas fumes sink? Hmm, well that's a wrench in that easy solution...arrg

 

[LeifThor]

during (correct) operation why would there be gas fumes in the engine compartment (or anywhere except out the exhaust) ?

Just realized I didn't really answer your question about the blower, and it's a great question by you.

Gasoline engines before they are started can accumulate gasoline fumes in the engine compartment. Gasoline fumes are much more dangerous than liquid gasoline as the fumes are far more combustible. There's a bunch of videos on Youtube of folks not running their blower before starting their engine and BOOM! So the blower clears any fumes out, so it's safe to start your gas engine. Diesels don't really require a blower, they're really primarily for gas engines, and they're very very important to use. Hope that helps.

 

[Kenneth K]

While she runs she runs cool as a cucumber, can put my hand on the engine and it's luke warm.

If you can keep your hand on your engine block/head/parts while it's running, you likely have another problem to solve. Should be near 185 degrees:

"the average person can touch a 140°F surface for up to five seconds without sustaining irreversible burn damage." https://www.electronics-cooling.com...electronics-products-appliances-vs-wearables/

 

[LeifThor]

If you can keep your hand on your engine block/head/parts while it's running, you likely have another problem to solve. Should be near 185 degrees:

"the average person can touch a 140°F surface for up to five seconds without sustaining irreversible burn damage." https://www.electronics-cooling.com...electronics-products-appliances-vs-wearables/

I replaced the exhaust system Kenneth (along with so very much more lol) and the engine runs very cool and effectively when running. It took 3 designs before I was happy with it (and do not EVER use galvanized pipe, use only black pipe). It's the manifold that's luke warm when the engine is running, runs like a champ, especially considering I've replaced the entire engine except the block including the tank and exhaust system, alternator, water pump yada yada, probably like most of us here lol.

 

[Kenneth K]

Maybe this will help (see link below). While the total thermal energy of the engine can only decrease after you shut it down, different parts of the engine will reach higher temperatures once the flow of coolant stops.

Perhaps it is a portion of your exhaust system that is overheating after shutdown, and not the engine itself.

Temperature rise a motor after shutdown - Heat Transfer & Thermodynamics engineering - Eng-Tips

In a forum I'm a part of there were a couple of people saying it would be okay to drive without a radiator fan in traffic as long as you turn the engine off at

www.eng-tips.com

 

[LeifThor]

Maybe this will help (see link below). While the total thermal energy of the engine can only decrease after you shut it down, different parts of the engine will reach higher temperatures once the flow of coolant stops.

Perhaps it is a portion of your exhaust system that is overheating after shutdown, and not the engine itself.

Temperature rise a motor after shutdown - Heat Transfer & Thermodynamics engineering - Eng-Tips

In a forum I'm a part of there were a couple of people saying it would be okay to drive without a radiator fan in traffic as long as you turn the engine off at

www.eng-tips.com

Thanks for the link Kenneth. For sure the black pipe section which is well wrapped gets hot during operation (it's the hottest part of the engine) and it stays hot too after the engine is off. But it's the engine block that really heats up after the engine is turned off that gets hot.

My neighbor asked me earlier today if I ran it in idle for a few minutes before turning the engine off, which I don't so now I will. Apparently if the engine isn't in gear, and just running idle, it will cool substantially to it's lowest operating temperature, so when I do shut it down, it will be cooling from the lowest instead of the highest (if I go from in gear to off), so I'll also be doing that too.

 

[Kenneth K]

In regards to the last photo: shouldn't the check valve face the other way?

 

[Dave G.]

It gets so hot, it's slightly melted the cushion on top (through the cracks between the engine cover the remainder of the seetee).

I can't picture the precise situation you are describing but maybe a aluminum heat shield 1/8" thick with an air gap(1/4") applied to the underside of the settee and close up the gaps with some hi temp gasket tape ?