Thinking out of the box

It's not a bad idea to have an exhaust blower in a diesel-engine compartment either. Or am I biased because I have one?

I do- I suspect it's more to remove heat after cruising.


1983 Present 42 Sundeck
Twin Lehman 135's

During cruising too....Lots of fresh, cool air makes diesels happy.....and more efficient.

Greetings,
Mr. m. You're biased. I have one as well. It's VERY seldom used.

RT Firefly said:

Greetings,
Mr. m. You're biased. I have one as well. It's VERY seldom used.

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Why don't you feel the need to use it?

In a diesel engine room the blowers are used to cool the engine room. Now to start an "anchor" style war-- since the blowers blow air out, do they compete with the engine for air when used underway?

N4712 said:

Why don't you feel the need to use it?

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I almost never use mine .....as a single in a big engine space, running in moderate temps at well below it's rated output probably isn't suffering from gulping high temp air in the engine room.

Plus I rarely run them because outside temps are so high I need to run them to keep the saloon cool.

I do use them to vent foul odor or temps when working in the space.

psneeld said:

I almost never use mine .....as a single in a big engine space, running in moderate temps at well below it's rated output probably isn't suffering from gulping high temp air in the engine room.

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I guess it makes sense in cooler climates. What is the normal temp of your engine room?

N4712 said:

I guess it makes sense in cooler climates. What is the normal temp of your engine room?

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Probably well less than 100 for all but a few days...

Remember for now I only travel in really cool temps.

On my old sportfish with 3208s...one summer run in a warm bay...even with the blowers on, the engines over tempted and wouldn't perform due to the heat.

I have 8 10 inch fans in my engine room on the sporty. 4 in and 4 out. Manual and auto/temp controlled. Big engines.

psneeld said:

Probably well less than 100 for all but a few days...

Remember for now I only travel in really cool temps.

On my old sportfish with 3208s...one summer run in a warm bay...even with the blowers on, the engines over tempted and wouldn't perform due to the heat.

Click to expand...

Yep, makes a big difference.

Ours normally runs 120, and will go 130+ w/o blowers.

We have an engine room air extraction blower. It was installed at the time the boat was built. It works fine but we almost never use it. At our cruise rpm on a typical summer day (70-80 degrees f.) our engine room temp with two FL120s in it is about 100 degrees.

The only time we sometimes use the blower is after shutdown on an abnormally hot day (90 degrees) to reduce the heat coming up into the main cabin.

First thing I do upon entering the boat after being away for a while is hit the blower switch. after a few minutes I go to exhaust vents on port side by opening slider at galley sink, lean out and smell the ejecting air. Then I pull back throw carpet open up one engine hatch in salon and smell inside the compartment as well as look around with bright flashlight. Then close the hatch. By time I complete this about ten minutes has passed with blower on and my nose knows. Then I plug into shore power and we proceed to load boat!


I also utilize blower before each start while out n' about... as well as often using my nose to tell the whole story. Being a gas powered craft "too careful" is not in my vocabulary... "being very careful" is!


Happy Blower Daze! - Art

hmason said:

In a diesel engine room the blowers are used to cool the engine room. Now to start an "anchor" style war-- since the blowers blow air out, do they compete with the engine for air when used underway?

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Yes of course they do. That is why you want to bring in cool air while the engine is running. Not suck air out.

Your blowers should either be reversible or you should have both air in and out blowers.

Pressurizing an engine space is a very poor idea.

It will flood the boat with engine aromas , and may help increase / spread an engine room fire .

Even the best ER blowers can nor remove enough air to raise the engines altitude and reduce power.

Blowers SUCK for a reason.

FF said:

Pressurizing an engine space is a very poor idea.

It will flood the boat with engine aromas , and may help increase / spread an engine room fire .

Even the best ER blowers can nor remove enough air to raise the engines altitude and reduce power.

Blowers SUCK for a reason.

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Fred - You mention Pressurizing??

Properly hosed/venter/sized ER blower pushing (sucking) air out transfers equal volume of flow-through outside air in through the open vents and hoses that connect to the outside. By pushing (sucking) air in you are doing similar regarding equal volume air transfer flow-through but in reverse mode. Via flow-through air system in an ER the blower is always pushing/sucking equal volume air at same time... only difference is from which direction it is pushing and from where it is sucking.

For several reasons and for best results of removing unwanted fumes or odors I believe the age-old process of a blower exhausting ER air to the outside is how it should operated.

YRMV - Art


PS: As intoned in the post below this one... It is better to have plenty more vent/hose size/availability for flow-through ER air than what the engine can exhaust at WOT and the blower can simultaneously move in/out. In other words, be sure to have more than plenty vents and hose for outside air into ER. At least that's how I see it!

Who said anything about pressurizing the space?

Engines are just big air pumps and in many cases the boat builders have not allowed for proper sized air vents. So the engines end up fighting to get the air they need. And since they will try and pull it from anywhere they can they can end up sucking the A/C air out of your living spaces. Ever see an engine room door slam shut behind you while the engines are running?

You want to set your intake blowers to balance the engines need for ambient temperature intake air so the engine space is only has perhaps slightly negative pressure. Or better yet a balanced pressure.

If your engines are creating significant negative air pressure in your engine room or space while they're running, then you sure don't need to be running any exhaust blowers. Because the engines are exhausting plenty of air on their own, they don't need any help.

Risk is always present when you work on anything for a living. Based on the owners willingness to address the host of problems with this boat will determine whether I work on it. This is a very small industry and reputation is everything, I can't afford to have the reputation for shoddy work.
One of the most unpleasant aspects of working on boats is having to tell someone their 25k boat needs 15k's worth of work.
Case in point, I was hired to cut two access hatches in the sole of a Harbormaster fiberglass house boat. Nice clean boat with a fresh interior,new Fritigo refrigerator, Force Ten gas range, Ironstone counters, Electroscan head. A nice Delta boat with gas vdrives. They felt they stole the boat for 25k. When I cut the forward access hatch I exposed the main frame supporting the pilot house. It was totally black with dry rot. These boats were built like the ski boats of the time. They choppered in the stringers and frames while the hull was in the mold and painted the bottom of the 1/2 inch shop plywood cabin sole with polyester resin and nailed the sole down with iron nails to the stringers and frames. Finished off the sole with a layer of mat on the top surface. Sealed tight with no ventilation except penetrations for wiring and plumbing. By the time I finished chasing rot I replaced the 1/3 of keelson five stringers , the frame and about 1/2 of the cabin sole. This means new floor coverings for the cabin sole, new bulkhead paneling in the sleeping cave. When the work is completed the boat is still worth 25k. All of this damage caused by a leaking water heater at some point in the boats life. Once I exposed the dry rotted frame., any marine surveyor would have flagged the dry rot devaluing the boat by an estimated cost of repair. Hopefully the owners get their money back through enjoyment of nice Delta House boat.

That has been my exact experience with every houseboat I have worked on, or so similar as to be scary.

I basically inherited an early 90's 21' Malibu Skier. When I tore into it rot galore in stringers and transom plywood stiffener. Tore most out and sold it as is with full disclosure to a guy ready to repair. Fcked-up way to build boats. So simple to do it correctly in first place.