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Thread: Air filter - does size matter?

  1. #1
    Advanced Beginner bgary's Avatar
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    Air filter - does size matter?

    My air filter is looking a little ratty. I did my usual beginning-of-the-year cleaning (basically blew it out with some compressed air).

    Last night I looked online to see what a replacement costs. And couldn’t find one like it (it’s a circular K&N clamp on). I can find smaller ones, taller ones, oval-shaped ones, but not a match.

    Current thinking is is that size and shape probably don’t matter, as long as it fits and doesn’t restrict air flow. So I’m leaning toward getting a narrower-but-taller one which, at least mathematically, has more intake area than the old one.

    But it thought I’d ask The Collected Wisdom: is there any downside to having a bigger air filter (i.e. one which -theoretically - would allow more air into the intake)?

    Bruce
    Last edited by bgary; 05-13-2019 at 05:20 PM.
    "Makana" (ex-Thelonious)
    1985 Ericson 32-III #604
    Makana blog: here

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    Senior Moderator Loren Beach's Avatar
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    Thumbs up Yes to more air

    When I was "into cars" as a sort of hobby many decades ago, lowered resistance to the air flow going into an engine was always considered a "good thing"....
    1988 Olson 34 #8
    Sail # 28400
    Betamarine 25 (new 2018)
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    Moderator Christian Williams's Avatar
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    That K&N was recommended by Maine Sail and is the one on my current boat. Not that he's infallible.

    I think it is intended to be oiled, maybe cleaned and oiled, periodically.
    Last edited by Christian Williams; 05-14-2019 at 08:37 AM.
    Thelonious II, E381 hull 513 (1984) Universal 5432
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  4. #4
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    I use K&N RU-2450 on my M25XP. Replaced original metal can filter that was missing actual filtering material in 2016. Did not notice any difference except feeling better about it.
    Still Crazy, E32-3, 1987

  5. #5
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    Stumbled onto this thread some time back. Interesting take on using a Kubota tractor filter.

    https://forums.sailboatowners.com/in...-quiet.156298/
    1987 34-2
    Tortuga
    Universal M25XP

  6. #6
    Senior Moderator Loren Beach's Avatar
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    Exclamation Air Cleaner Caution

    Not to get all dramatic on you, but if *anyone* has one of those Universal filter assemblies with the aluminum mesh inside, Remove that mesh. Immediately.

    This applies to the M25XP and possibly the M25. Not sure if Universal used this on their other engines, and I know of owners who say their filter does not have this. (Or a prior owner removed it).

    http://www.ericsonyachts.org/infoexc...&referrerid=28

    http://www.ericsonyachts.org/infoexc...&referrerid=28

    While we will not know, sort of for sure, until the recipient of my old engine tears it down, my mechanic said that our crankcase blow-by problem for many years was likely caused by cylinder scoring from the pieces of that original mesh getting sucked in.

    I would advise anyone with an 80's engine from this series to overhaul their air cleaner... or just replace it with a K&N.
    Last edited by Loren Beach; 05-14-2019 at 06:35 AM.
    1988 Olson 34 #8
    Sail # 28400
    Betamarine 25 (new 2018)
    Fresh Air
    Portland, OR USA

  7. #7
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    Interesting. I have my "air cleaner" off while I replace the timing gear cover. The air cleaner is nothing more than an egg-shaped metal box with a small mesh screen at the pointed end of the box. Anything smaller then about 1/16" diameter would get right into the engine I imagine? I think adapting any sort of air filter would be better than this thing? And this small mesh screen is nearly blocked with grease from the "breather" tube which Universal re-routed to under the air intake screen (the tractor shows it pointing down to grease the farm I guess). I suppose that's better than the bilge but now needs some cleaning.

    For the people that have adapted an auto style cone filter.. what did you do with the breather tube?

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  8. #8
    Moderator Christian Williams's Avatar
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    A cable tie directs the breather tube against/into the filter.
    Thelonious II, E381 hull 513 (1984) Universal 5432
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    Principal Partner bigd14's Avatar
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    I threaded a brass hose barbed elbow into the rubber portion of the K&N filter and ran the breather tube to that. I believe I got the idea from Maine Sail's website.
    1984 Ericson 30+
    Hull #651

    Formerly 1972 Ericson 27

  10. #10
    Principal Partner Kenneth K's Avatar
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    K&N RU-2450 Universal Clamp-On Air Filter: Oval Straight $39.99
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    That's about $12 more than the first one I bought a few years ago. Buy the K&N filter cleaner and you can clean and re-use.

    Like Bigd14 said, you can drill and screw a hose barb into the flat underside and connect the breather tube directly to the filter.

    Ken
    '85 E32-3 "Mariah" #641
    Universal M-25

    "Saltwater is the cure; sweat, tears, or the sea......"

  11. #11
    Contributing Partner kiwisailor's Avatar
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    Quote Originally Posted by Kenneth K View Post
    K&N RU-2450 Universal Clamp-On Air Filter: Oval Straight $39.99
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

    That's about $12 more than the first one I bought a few years ago. Buy the K&N filter cleaner and you can clean and re-use.

    Like Bigd14 said, you can drill and screw a hose barb into the flat underside and connect the breather tube directly to the filter.

    Will this size filter fit the Universal 5432?
    Sherene & Mike Taniwha

    1981 E38 "KIWI"
    Hull #53
    Groton, CT

  12. #12
    Principal Partner Kenneth K's Avatar
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    Quote Originally Posted by kiwisailor View Post
    Will this size filter fit the Universal 5432?
    You'd have to measure your intake tube size (and maybe top and side clearances) to know. Its a slip-on fit for an M25 in an E32-3.
    Ken
    '85 E32-3 "Mariah" #641
    Universal M-25

    "Saltwater is the cure; sweat, tears, or the sea......"

  13. #13
    Advanced Beginner bgary's Avatar
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    Quote Originally Posted by Kenneth K View Post
    Its a slip-on fit for an M25 in an E32-3.
    Yes. Don't know about the M25XP, but the intake on my M25 is 1-3/4" in diameter, so any slip-on with a 1-3/4" ID flange will work.

    I like the K&N stuff too.

    Bruce
    "Makana" (ex-Thelonious)
    1985 Ericson 32-III #604
    Makana blog: here

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    I ran my breather hose down into a clear recycled plastic bottle zip tied onto one of the fwd engine mounts (M-18). This keeps the filter a bit cleaner and collects the very small amount of oil from the hose. Not sure if removing it from the air flow makes much difference to the engine … PCV is an emissions feature is it not?

  15. 05-16-2019, 09:14 AM

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