Engine Compartment Blower

[Mark Myns]

I have a 38' Marine Trader Sundeck with a single 135 HP Ford Lehman diesel. There are two engine compartment blowers and I have not figured out why they are there with a diesel engine. I do have a generator but it is also diesel. I would never put any type of flammable fluids in the engine compartment. My question is if there is a good reason not to remove these blowers? They are in the way of several things I am working on and getting rid of them would make some work easier and more accessible. In the five years I have owned the boat I have only turned them on once when I bought the boat.

 

[greysailor]

I have a 38' Marine Trader Sundeck with a single 135 HP Ford Lehman diesel. There are two engine compartment blowers and I have not figured out why they are there with a diesel engine. I do have a generator but it is also diesel. I would never put any type of flammable fluids in the engine compartment. My question is if there is a good reason not to remove these blowers? They are in the way of several things I am working on and getting rid of them would make some work easier and more accessible. In the five years I have owned the boat I have only turned them on once when I bought the boat.

Welcome aboard Mark!
Down here in Texas, they are for heat removal! ?

 

[Lepke]

People use blowers to exhaust the engineroom heat after running.

 

[bligh]

I would actually like a good one in my engine room for the summer heat , especially after i shut down.

You can certainly remove them. There is no reason to have them other than heat removal. But you will see members here who install them in their diesel engine rooms just for that reason. Maybe lemans run at such low rpms they never heat up. haha

 

[O C Diver]

I have a 38' Marine Trader Sundeck with a single 135 HP Ford Lehman diesel. There are two engine compartment blowers and I have not figured out why they are there with a diesel engine. I do have a generator but it is also diesel. I would never put any type of flammable fluids in the engine compartment. My question is if there is a good reason not to remove these blowers? They are in the way of several things I am working on and getting rid of them would make some work easier and more accessible. In the five years I have owned the boat I have only turned them on once when I bought the boat.

If you don't have an engine room temperature gauge, you might want to buy a simple digital one that remembers maximum temperature. Install it near the ceiling and see what sort of temperatures you're getting after a day of cruising. Cooler is better, but over 125 degrees may be concerning.

Also, if you get engine room smells in the saloon after shut down, running the blower for 20 or 30 minutes usually eliminates that.

Ted

 

[BruceK]

MM, do a 1 hour comparison runs, with and without. I doubt you`ll need a thermometer to tell you that "without", the ER is appreciably hotter. I use my exhaust blower whenever running,(except if I forget). As air is expelled,I figure the vent on the other side draws replacement air.
Interesting you have two, presumably one for intake and one to expel, could be overkill.

 

[DavidM]

Realize that a diesel engine itself is a pretty good bilge blower. Running at 1,500 rpm a 5.8 liter engine sucks in about 150 CFM of air, burns it and blows it out of the exhaust. It doesn't matter if it is running very lightly in neutral or heavily loaded underway. A diesel sucks in the same amount of air for each other revolution no matter what. It takes a heavy duty bilge blower to keep up with that flow rate.

Bilge blowers are used on diesels principally to cool down the engine room after shutdown and generally not for keeping the engine room cooler while the engine is running. If you do need to keep the engine room cooler while running it probably means you don't have enough vent inlet area which is starving the engine of air and it probably is smoking as a result.

So if you don't need to cool down the engine room after shutdown, remove the blowers. Lots of diesel boats don't have them.

David

 

[Irish Rambler]

Just my two penn'orth.
If you wire your bilge blowers into your ignition you'll help the engine get cleaner cooler air and keep the bilges aired from any smells when underway.
Engine room smells are also a contributing factor if anyone's prone to seasickness. We've found that chewing a piece of crystallised ginger half an hour before casting off help to settle the stomach and prevent it.

 

[Comodave]

How are they hooked up? Do they exhaust from high or low in the engine room?

 

[Ski in NC]

I have one exhaust blower in my ride. On a hot summer day if I anchor and shut down the main, then start the gennie for AC, the back end of the gennie gets HOT, as the back end is air cooled. So then I run the blower just to get some air exchange in the engine room space.

It is unique in the blower is small, but jets into one engine room vent plenum for a bit of a venturi effect. Moves much more air than the blower itself.

That's the only time I run it. If main is running, it naturally moves much more air as Dave noted.

Some boats could come with gas engines, and so many boats put blowers in anyway as the gas/diesel decision has not been made at that point.

 

[fractalphreak]

Realize that a diesel engine itself is a pretty good bilge blower. Running at 1,500 rpm a 5.8 liter engine sucks in about 150 CFM of air, burns it and blows it out of the exhaust. It doesn't matter if it is running very lightly in neutral or heavily loaded underway. A diesel sucks in the same amount of air for each other revolution no matter what. It takes a heavy duty bilge blower to keep up with that flow rate.

Bilge blowers are used on diesels principally to cool down the engine room after shutdown and generally not for keeping the engine room cooler while the engine is running. If you do need to keep the engine room cooler while running it probably means you don't have enough vent inlet area which is starving the engine of air and it probably is smoking as a result.

So if you don't need to cool down the engine room after shutdown, remove the blowers. Lots of diesel boats don't have them.

David

+1 I find that my twin 120 Lehman's ventilate the engine room well when running; I have a fire discharge port that when I open it i note a slight negative pressure there- its in my aft engine room bulkhead- (i.e. can detect a draft into the engine room). On hot days we notice a difference AFTER the engines are shut down in that the salon stays cooler (or rather doesn't heat up as much) if we run the blower for 40 min or so.

 

[BruceK]

+1 I find that my twin 120 Lehman's ventilate the engine room well when running; I have a fire discharge port that when I open it i note a slight negative pressure there- its in my aft engine room bulkhead- (i.e. can detect a draft into the engine room). On hot days we notice a difference AFTER the engines are shut down in that the salon stays cooler (or rather doesn't heat up as much) if we run the blower for 40 min or so.

Interesting to read that. My IG36 has vents either side, plus a separate vent one side for the exhaust fan, which has its switch right next to the engine switches. It`s way cooler down there with the exhaust fan on compared to off, puts out a good volume of air. The day of a 5 hour run the day I forgot it, ER was unpleasantly hot.