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Old 10-04-2017, 09:23 PM   #1
seasalt007's Avatar
City: Punta Gorda, FL
Vessel Name: Aweigh
Vessel Model: Nordic Tug 42
Join Date: Jun 2014
Posts: 628
Generator with No Air Filter

I was surprised to learn that many generators do not have an air filter. My Onan 11.5 is one of them. It has something that could be mistaken for a filter but it is an intake resonator.

I had a minor exhaust leak on the main engine that eventually clogged it's Air Sep so I figured I would clean the generator's air filter. Several calls went to Cummins dealers who had no clue where it was and didn't mention the resonator. Finally one Ft. Lauderdale dealer said that many do not have an air filter and that the suspicious black box in my picture was a resonator on the air intake.

Who knew??
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Old 10-04-2017, 09:35 PM   #2
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City: Between Oregon and Alaska
Vessel Name: Charlie Harper
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Many marine diesels don't filter air because it is assumed they operate in clean air. Some items that appear to be air cleaners are filled with sound absorbing material. The intake makes more noise than a gas engine because it's always wide open. No throttle plate.

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Old 10-05-2017, 07:22 PM   #3
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City: Brookline, NH
Vessel Name: Blue Heaven
Vessel Model: Albin 43 classic double cabin, twin 135 Lehmans
Join Date: Sep 2013
Posts: 2,054
My NL generator has an air box with something "like" a filter, but it is so coarse all it would stop are tools and loose nuts and bolts. The "filters" on my Lehman 135's are about the same and they have no problem running many thousands of hours. Guess there just isn't much dirt to ingest.

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Old 10-05-2017, 07:38 PM   #4
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City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
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If you go through the Suez canal in a dust storm, get a filter. And yep, most gennies just have a silencer. Some mains are similar.
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Old 10-05-2017, 08:05 PM   #5
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City: Cape May, NJ and Englewood, FL
Vessel Name: Irish Lady
Vessel Model: Monk 36
Join Date: Dec 2007
Posts: 3,913
No air filter on Westerbekes. My Perkins main engine does not have one either. Just a flame arrestor screen to keep the flamer pre-heater in check. My flamer is disconnected.
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1984 Monk 36 Hull #46
Currently in Cape May NJ
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Old 10-05-2017, 08:11 PM   #6
City: Northport
Join Date: Aug 2015
Posts: 1,841
I added a K & N filter to each of our past Westerbeke gensets at the end of that resonator - quite easy as that resonator has a round outlet similar to a throttle body outlet. Many years back I added a K & N filter to my Perkins 165 and a Lister Petter genset engine as well.
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Old 10-07-2017, 03:23 AM   #7
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City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
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Posts: 3,432
Ours never had one, just a big hole sucking in air.
Got one of these thinking it was 100% better than nothing and only $5

Not the exact size I got but various other sizes available for the same $
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Old 10-07-2017, 06:22 AM   #8
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City: Freeport Tx
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My didn't have one just got a kn filter cleaned it once a yr
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Old 10-07-2017, 07:49 AM   #9
City: Carefree, Arizona
Vessel Name: sunchaser V
Vessel Model: DeFever 48
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A foam air filter is quite common on gensets with appropriate cleaning instructions in the manuals.
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Old 12-16-2017, 05:52 PM   #10
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City: Baltimore
Join Date: Sep 2017
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I use a K&N # RU-0210 air filter on my 8kW Onan. Fits perfectly.
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Old 12-17-2017, 03:28 PM   #11
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City: Inside Passage Summer/Columbia River Winter
Vessel Name: Alaskan Sea-Duction
Vessel Model: 1988 M/Y Camargue YachtFisher
Join Date: Jul 2012
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My 1988 Onan 8KW does not have an air filter on it. Why not? Is there a reason Onan/Kubota does not have intake filters. Does adding one affect performance?

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