Air filter - does size matter?

bgary

Advanced Beginner
Blogs Author
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
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
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".... :nerd:
 

Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
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.
 
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sharonov

Member II
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.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
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. :eek:

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/infoexchange/showthread.php?11781-Universal-XP25-failure-caused-by-airfilter&referrerid=28

http://www.ericsonyachts.org/infoexchange/showthread.php?10244-M25XP-Air-Intake-woes&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.
 
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debonAir

Member III
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?

airintake.jpg
 

bigd14

Sustaining Member
Blogs Author
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.
 

kiwisailor

Member III
Blogs Author

bgary

Advanced Beginner
Blogs Author
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
 

Second Star

Member II
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?
 
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