Blower for Diesel - SailNet Community
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post #1 of 6 Old 02-19-2007 Thread Starter
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Blower for Diesel

I've got a Ranger 33 with a Universal 4-30 diesel. I recently bought the boat in October and was aware at the time that the blower didn't work. I was also aware of some electrical problems. While cleaning up under the cockpit I came across the old blower which was mounted just under one of the cow vents. Suffice it to say, it was very rusted out. Tracing the wiring, I came to realize that this was the cause of the electrical problems. No fuse and the motor rusted out, shorting and causing excess heat...melting some of the wires.

Anyway, I've removed and cleaned the wiring up, replacing as needed. I've read that blowers for diesels are good to improve reliability. I've read that the blower needs to "pull" air out of the compartment. The question I have is how should I mount the blower? I have two cow vents. It seems to be they are a potential entrance point for water either from rain or waves from the aft. Should I put a blower on both vent? I read about putting a filter at the input of the compartment to prevent water, salt and other contaminents from getting into the engine compartment. Anybody have any good information for the creation of this? Any good links?
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post #2 of 6 Old 02-19-2007
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With the blower in place as you described it's likely the boat was repowered at some point and initially had an Atomic 4 gas engine, for which the blower was essential. It likely wasn't used since the repower, hence the deterioration of the blower motor.

That said, using a blower on a diesel, while not technically required to remove potential explosive vapours, is not a bad idea. Pulling air from the engine space will minimize heat buildup and may also help to keep the inevitable diesel engine odours from permeating the cabin space.

Given that your cowl vents are likely atop the transom in typical Ranger fashion, I think the likelihood of serious water ingress is mimimal under normal sailing and weather conditions. Should you find yourself in extreme conditions it would be prudent to wrap/block the vents for the duration.
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post #3 of 6 Old 02-20-2007
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I put an exhausting blower in my diesel-engined boat. You wouldn't believe how hot the exhausted air is! I'm very happy, thinking of how much cooler everything in the engine room is now.

You really want the blower _exhausting_. If you push air into the engine room, you'll have "engine room smell" coming out around doors and hatches into the boat's passenger spaces -- not good. Better to pull the air out through one of the vents, so the engine room is under (very slight) vacuum.

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post #4 of 6 Old 02-20-2007
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The only problem with having the engine room under slight negative pressure is that you may end up starving the diesel for air. They are very air hungry when running...


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post #5 of 6 Old 02-20-2007
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Hey TJ, blowers work wonders for the odors and a slight temperature reduction during warm weather. Our Mistress came with an engine room blower and is powered with a 4-107 so they aren't just for gas-engined boats. If you have room for ducting you can put the pickup wherever you like. If not the circulation patterns may be a little less than what you want but all things being a compromise..... Bill Seifert's book " Offshore Sailing" shows the installation we use. We have 4" non-metallic duct and a blast gate mounted on the inside of the coaming to prevent water ingress when conditions warrant. System has worked flawlessly for over 3 years now. Components came from Pennstate Industries but are probably available from others as well. Good luck with the project.
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post #6 of 6 Old 02-20-2007
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Blower was factory equipment on my diesel powered boat set to exhaust out one vent, other vent also has hose leading to engine compartment to provide air intake. I've been in some pretty large following seas and can't see a problem with water intrusion on a moving boat with a following sea. More likely to happen if the boat was secured and got slapped on the transom by a steamship wake.
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