Ventilation

[Pure pleasure]

Do you run the blower all the time with a diesel I have a 48 krogen.

 

[kelbylinn]

Nope. Only when we drop anchor on our 42 GB with Detroit 453's. That's to help the cabin a.c. keep things cool. Don't use it at all when underway.

 

[markpierce]

We use the engine compartment's ventilation fan when entering the compartment after running the engine. Nevertheless, it's still quite warm in there. I don't view the fan as a necessity as the heat doesn't enter living spaces.

 

[Bob Cofer]

We run it all the time in our GB 32.

 

[BruceK]

When the L120s are running.
It`s not a fume/safety issue, it`s for cooling, gets a lot hotter in there without using the exhaust fan which is mounted one side of the hull below vents, with reciprocal vents on the other side.

 

[Peter B]

I don't have any ER ventilation other than the built-in (large) vents. Nothing blown, as not needed for safety in a diesel, like it is with petrol (what you call gas) engines.

 

[caltexflanc]

Depends on the boat design. For instance my Hatteras had a DC blower that vented the battery area(s) which the manual said to run when below ('cruising speed"). The duct inlet was low, along the battery boxes. It also had a set of AC blowers, mounted high along the ER ceiling, which were designed for cooling the ER for working in it, or evacuating the CO2 if the fire system had tripped. BTW, each engine was in its own room with 6'4" headroom.

A diesel engine is one big "blower" in and of itself.

 

[O C Diver]

Run mine whenever the engine is running and uo to a half hour after shutdown. Reduces engine room temperature, battery temp, fuel temp, cabin temp above engine room, and keep any smell from coming out of the engine room when I open the hatch to do a check while underway. Have one 220 cfm blower. Consider it important enough that I have a spare.

Ted

 

[tadhana]

On a diesel boat the primary use of an engine room blower is to exhaust heat during heat soak after shut down. When underway, Itf the air intake area is minimal, you can actually spin the blower backwards due to the pressure drop in the engine room. Many electronics such as inverters do not like to be exposed to high heat. . The blower is there to protect that equipment

 

[FlyWright]

My boat with twin Perkins 4.236's doesn't have ER blowers/fans. Not needed.

 

[Pure pleasure]

Well cked the temp it was 91 going in the vent and 123 coming out that was with blower on for 3 hrs that we were running

 

[tadhana]

After we get in we turn on the blower and run it till the engine room gets down to 90 degrees. Today, that might mean we run it till midnight. Bloody hot here on the Chesapeake today.

 

[dhays]

Interesting information. I have typically not run the blower on my boat. My thought was that the engine's air intake is providing a lot more air exchange than the blower does anyway. However, maybe I am wrong on that. The other issue is getting rid of the heat after shut down, something I hadn't though of either.

I have some very long runs ahead of me over the next week (12hours or so). I suppose that with the heat buildup in the fuel tanks (that flank the ER) as well as the heat soaking of the ER from a very long run, every little bit of venting could help?

 

[tadhana]

You probably have a fuel cooler so that the build up in the fuel temp will not be that critical. At low rpm the blower might removes some heat but at high RPM it could actually reduce the performance by increasing the engine room air depression which makes harder for the engine to get combustion air. Best to let the engine be the fan underway and let the blower manage waste heat when you stop.

 

[hmason]

uh oh.

 

[O C Diver]

You probably have a fuel cooler so that the build up in the fuel temp will not be that critical. At low rpm the blower might removes some heat but at high RPM it could actually reduce the performance by increasing the engine room air depression which makes harder for the engine to get combustion air. Best to let the engine be the fan underway and let the blower manage waste heat when you stop.

There are a lot of us with modern engines that don't have fuel coolers. Properly sized engine room air intakes pose no problem for adequate air flow for both engine and exhaust blowers. Reduced combustion air temperature is beneficial to engine performance and fuel economy. Best to consult the boat builder regarding using the ventilation underway, some specify it. After all they were the ones who designed and built the space.

Ted

 

[dhays]

You probably have a fuel cooler so that the build up in the fuel temp will not be that critical. At low rpm the blower might removes some heat but at high RPM it could actually reduce the performance by increasing the engine room air depression which makes harder for the engine to get combustion air. Best to let the engine be the fan underway and let the blower manage waste heat when you stop.

Good points. I think you have a 330hp Cummins 5.9l QSB? I have the 380hp version. There is a fuel cooler on my engine, and given this application, it is likely to be completely unnecessary. Since it is there, I probably won't see much fuel temp increase over time.

Not sure about the air pressure issue, I don't think the blower has that much capacity and the air intakes into the ER seem to be plenty large.

Turning on the blower after engine shut down makes sense. Of course that means that I have to remember to turn it off as well.

I would love to find a 12v timer switch that could be toggle on and then shut itself off after 30 minutes. I can think of a couple uses for that.

 

[O C Diver]

I would love to find a 12v timer switch that could be toggle on and then shut itself off after 30 minutes. I can think of a couple uses for that.

Intermatic spring wound timers Time range from minutes to hours.

Buy the commercial grade (FF). The Decorator grade (FD) is price point junk.

Ted

 

[tadhana]

Dave, I figured your boat probably had a Cummins and she is of about the same vintage as ours with QSB 5.9 230. I ran a well known boat yard and we were a Cummins servicing dealer. Engine room depression is more common than people realize. A diesel consumes a lot of air. If you are going to put a timer on the engine room fan, it probably needs to be set for hours, not minutes. Granted your ambient air and water are cooler than ours (83 degree water right now). To get our engine room below 100 degrees we often have to run the fan for 4-6 hours in the summer time. In the winter with 45 degree water we don't run it much at all.

 

[Rossland]

Many electronics such as inverters do not like to be exposed to high heat. . The blower is there to protect that equipment

We have a fan and duct that blows outside air on the inverter/charger. It is controlled by a thermostat set to come on at 95F. It runs most of the time while cruising, and usually for a couple of hours after shutdown, depending on outside temperature.

 

[BruceK]

Interesting information. I have typically not run the blower on my boat. My thought was that the engine's air intake is providing a lot more air exchange than the blower does anyway. However, maybe I am wrong on that. The other issue is getting rid of the heat after shut down, something I hadn't though of either.

I have some very long runs ahead of me over the next week (12hours or so). I suppose that with the heat buildup in the fuel tanks (that flank the ER) as well as the heat soaking of the ER from a very long run, every little bit of venting could help?

You have an opportunity for comparative testing, by running the boat with and without the blower operating. If you do, conditions of operation will need to be as similar as you can get them to provide fair comparison.

 

[dhays]

Intermatic spring wound timers Time range from minutes to hours.

Buy the commercial grade (FF). The Decorator grade (FD) is price point junk.

Ted

Those would work well. As long as I can find a place to mount them that would be acceptable to my wife. I could put them in the ER, but they wouldn't be super convenient at that location.

 

[dhays]

Dave, I figured your boat probably had a Cummins and she is of about the same vintage as ours with QSB 5.9 230. I ran a well known boat yard and we were a Cummins servicing dealer. Engine room depression is more common than people realize. A diesel consumes a lot of air. If you are going to put a timer on the engine room fan, it probably needs to be set for hours, not minutes. Granted your ambient air and water are cooler than ours (83 degree water right now). To get our engine room below 100 degrees we often have to run the fan for 4-6 hours in the summer time. In the winter with 45 degree water we don't run it much at all.

True. Water temps hover around 50 degrees F and if air temps are in the 80's we consider it way too hot.

 

[Pgitug]

Does anyone have pictures of the fan/air pickup duct? Some fans I have seen pickup under the diesel engine, which seems out of place. (Heat Rises). And where is your discharge?

 

[psneeld]

Does anyone have pictures of the fan/air pickup duct? Some fans I have seen pickup under the diesel engine, which seems out of place. (Heat Rises). And where is your discharge?

Diesel boats usually remove air from the top of the space or right over the engine.

Under is a gas boat setup usually.

 

[O C Diver]

My setup:

The original install on mine was really bad. There were 4 blowers running through clothes drier vent hose. The hose wound all over the place and was partially crushed is a number of spots. Very minimal flow. I redid the 4" drier hose with 5" fiberglass exhaust pipe and sweep exhaust rubber 90s. It goes though the rear engine room bulkhead near the ceiling, along the ceiling of the lazarette, and out through the transom below the swim platform. There is a water block where the pipe turns up in the hollow transom, going most of the way to the cap rail. The blower mounts to the 5" pipe with a 4" to 5" flexible coupling which eliminates vibration. The purpose of the 5" pipe (over 4") is to eliminate frictional line loss. It is amazing how well it works! The one blower produces more flow than the previous 4. You can see ripples on the water out to 2' from the force of the air coming out of the blower. The blower is worth 10 to 15 degree temperature reduction in the engine room measured at the ceiling. So far, temperatures have stayed below 100 degrees with the ventilation on. Outside air tracks into the engine room through the hollow keel and rises in front of the engine.

Blower (yellow fan blades) going through stern engine room bulkhead.



Blower pipe exiting transom on port side under swim platform. Engine exhausts is on the starboard. The water block goes above the rub rail before turning back down.



Ted

 

[Deckape]

Run the blowers (4) anytime engines are operating and for an hour or so after shutdown. Two bring air in and two exhaust hot air . Notable difference when not run after shutdown. Keeps engine room cooler and exhaust any smells and heat.

 

[tadhana]

Our two blowers are mounted high, at the aft end of the engine they are ducted out to the same plenum that the engine air draws in through.