Diesel engine blower?

[RickBowman]

Most of us probably know why a gasoline inboard needs a blower, right? Diesels are not known to blow the top of the boat off unlike their gasoline guzzling redheaded stepchilds do. Why bother with a blower? Is it really necessary? Do you really motor that much? Why have a sailboat if the engine and hence the motor is constantly running? Go on ahead to the dark side, go to the land of See Ray. With that said, I do have a blower because PSC or ???? installed it. I put a switch on the circuit due the unbelievable racket that the little air pusher produced. Oh well, folks in glass houses shouldn't throw parties, right?

[sailingdog]

Rick-

There are many reasons that installing a blower in a diesel engine compartment make sense.

1) It helps the engine breathe properly
2) It helps vent excess heat from the engine compartment, and can help keep the boat cooler in the summer time.
3) It helps keep the smell of the engine out of the interior of the cabin
4) It helps keep the alternator cooler, which will increase its efficiency and extend its life.

[RickBowman]

sailingdog,
I guess we can agree to disagree on this one. My sailing, not motoring for extended periods of time, occurs in fresh northern waters with cool to cold water. My engine compartment is not airtight and for a little 3 cylinder diesel needs no additional air. I have no smell, if I did then I have an engine problem, leaking fuel, leaking exhaust or leaking oil that would need to be addressed and corrected. The altenator is designed for engine heat. I have not had a problem nor do I expect one with the current setup.

[sailor25b]

As for me, I will install my blower tomorrow. I look forward to a cooler aft berth, and the elimination of the slight smell from my 20-yr old engine that seems worse on hot days.

Yes, it's a sailboat and I am a sailor, but I am not ashamed to crank up "Ol' Bessie" when I need to.

As I think about tomorrow's installation, the numerous possibilities have me reeling. I'll attach the blower to the existing 3" duct pipe that leads to an aft cowl. I think I'll run the power and ground lines through the main panel to a dedicated switch, but I wonder if I should run the hot wire to the ignition circuit so the fan runs with the engine? Any advice there? Also, Should I run a separate switch to the cockpit? Where in the line should I put the fuse?

[Hawkeye25]

You really need to consider which blower and how to plumb it. I've installed many for customers, but all were on big powerboats that began to suffer for horsepower in steaming hot Naples. As engine room temperatures soared, horsepower fades because the engine intake air is less dense and expands less in combustion. I used the inline 4" blowers to take air from outside and blow it straight at the engine air intakes, resulting in the engines again being able to make proper peak RPM's to get up on plane. The blowers are keyed to the engine 'run' position through constant duty solenoids. Engine room exhaust is not blown, but is ducted out from as high in the engine compartment as possible to get the hottest air first. An auxilliarly switch can be rigged on the console to cool the engine room after shutdown, but it should be either set on a timer or be accompanied by a large, annoying red light to keep you aware that it is on.

In a tight engine room, air in equals air out and engine combustion is a large part of that process, so the blowers on a big powerboat cannot possibly keep up with two big diesels at full song, though they do help performance. In a sailboat with less than 100 HP (most have 30 - 60) a single 4" blower is more than enough. I have a tendency to treat horsepower and engine health first, and engine room ventilation as a happy by-product. It still works.

[sailingdog]

Originally Posted by RickBowman

sailingdog,
I guess we can agree to disagree on this one. My sailing, not motoring for extended periods of time, occurs in fresh northern waters with cool to cold water. My engine compartment is not airtight and for a little 3 cylinder diesel needs no additional air. I have no smell, if I did then I have an engine problem, leaking fuel, leaking exhaust or leaking oil that would need to be addressed and corrected. The altenator is designed for engine heat. I have not had a problem nor do I expect one with the current setup.

Works for me.. but just because an alternator can work in a hot environment, doesn't mean that cooling that same environment won't make the alternator work better and last longer.

[hellosailor]

Rick-
"The altenator is designed for engine heat." Ideally, yes. But if you look at the service bulletins and installation notes for alternators in general? Reality bites. A marinized alternator needs dual fans to compensate for not having the generous airflow that a car or truck has. Not all conversions get that right. And even then, as an alternator (or most other electronics) runs hotter, the time between failures goes down, the output goes down...An engine can run damn hot, remember the block is trying to run at thermostat temperature (140-180F) and the the side near the exhaust manifold will be running in heated air as well.

Not that I'd run a bilge blower all the time to cool the alternator! Just pointing out that alternators, like other valued household staff, perform better as they get closer to 74F.

[T37Chef]

Originally Posted by sailor25b

I could attach it to a ventilation hose that leads aft.

Think about where that hose goes through the boat?

Arguably, one of the best places would be in the cockpit under something, so that if caught in rough seas water does not easily enter through the opening. A 4" hole could fill a boat pretty quickly You can see were mine in this photo link, located just to the right/bottom of the engine gages

click link for image:

http://newimages.yachtworld.com/1/5/...?1158931582000

[hellosailor]

T37-
"A 4" hole could fill a boat pretty quickly" You mean, everybody doesn't have ball valves or fill plates handy, to secure their engine compartment vents in rough weather?!

[RickBowman]

As the complexity of a system approaches infinity, the time between failures approaches zero.