Dissolved Air Filter

[ToddS]

I have a 2004 Beneteau 373 with a Yanmar 3ym30 engine. I bought it last year from the original owner, and I (am learning how to) do most maintenance myself.

In went to inspect the air filter, and found the filter foam (which normally surrounds the metal frame) to be almost completely GONE! (see photo)

I (obviously) replaced it with a new filter, but I'm wondering if anyone could advise on what caused this. I have 4 theories:

1. At some point a rodent climbed aboard while the boat was on the hard, and found its way into the intake and stole the foam for nesting material. I've seen rodents do this with foam in car engine compartments, and materials in my garage... but never on my boat. I would think I would find other evidence of rodent infestations, but maybe not if it happened years ago, and was otherwise cleaned up by the previous owner. Seems unlikely though.
2. Vapors from some fuel or solvent dissolved it. Seems possible... open cell foam is pretty fragile stuff, and I could easily imagine fuel vapors, or acetone, or WD40, or something dissolving the foam... I just don't know what... and again, it was probably something from years ago, with a previous owner. Generally though, the engine compartment is very clean and well maintained... no real evidence of chronic leaks/fluid/solvents/etc causing problems with other nearby soundproofing foam, or hoses, or anything else. The engine is in EXCELLENT shape, with only a few hundred hours on it. Starts quickly and easily every time, so I wouldn't think there was ever a need for someone to use starting fluid, etc... which would likely cause this... but again... previous owner, so I can't say 100% for sure... I guess that's my hunch, but it doesn't really fit with what I know about the previous owner (kept things is great condition pretty consistently).
3. Just plain old... Maybe the previous owner never checked it for 15 years (the age of the boat) and maybe that's what happens to foam if you leave it unchecked in a hot engine compartment for that long.
4. I'm missing something - not being a diesel mechanic... it is possible and actually very likely that I'm missing something.

For now my plan is to keep an eye on the new one periodically, and make sure it is just something from the past (which I strongly suspect is the case)... but i'm just curious if anyone has encountered this and can help solve my riddle...

 

[Justin_NSA]

Mine was like that when I bought it also. Not sure what the rate of decay is.

 

[Don S/V ILLusion]

Not an uncommon problem. These filters as a solution to a problem which doesn’t normally exist, I.e., engine compartments and the area from which air is drawn isn’t dusty. The filter material, once dried out and under constant heat, can and as you noted, does deteriorate and gets sucked into the engine causing a potential problem where none previously existed.

Note that many marine engines have no air filter for this reason.

If you have a problem with belts causing dust, it’s better to fix the belt problem.

 

[Richard19068]

You might try going with a K&N filter and not worry about foam breakdown.

 

[BigEasy]

My boat also has a 3YM30. Was 6 years old when I purchased with low hours. I found the filter in same condition as yours. Suspect heat & age are main factors in the foam deteriorating.

 

[thinwater]

...Note that many marine engines have no air filter for this reason....

I've been studying used oil filters for another project. Guess what the most common macro contaminants are?

• Fiber shed from the oil filters.
• Plant particles, including pollen and bug parts.
• Other unidentified, which probably includes belts and engine room fibers.

Engines suck up a LOT of air. And yet, I've got to believe they have tested vehicle-style filters on them many times.

 

[thinwater]

My boat also has a 3YM30. Was 6 years old when I purchased with low hours. I found the filter in same condition as yours. Suspect heat & age are main factors in the foam deteriorating.

As I recall, the manual says to clean the foam ~ 250 hours. But why not use a tractor filter? Is there an actual reason, other than the assumption it might not be needed. If the foam only lasts 4-8 years before sucking into the engine, that sounds bad, or at least pointless.

 

[Justin_NSA]

When you think about it. Whatever it has trapped over time will eventually get sucked in anyway if you let it dissolve.

 

[Project_Mayhem]

This type of foam deteriorates over time even when guarded from UV, heat and moisture. Throw those elements back in the equation with some additional mechanical forces from sucking air through them and the life gets even shorter

 

[ToddS]

You might try going with a K&N filter and not worry about foam breakdown.

Thanks all for reassuring me... I hadn't seen this before, but I'm more accustomed to paper automotive style filters, or K&N cleanable filters (which I use happily and successfully in my car). I don't K&N makes a filter that is an exact fit for my Yanmar... if they do, I didn't notice it in my quick visit to their site... otherwise I'd go that way. Okay... so my takeaway is that this is common... and that I should check on my replacement one more often and replace it before it (and all of its captured contaminants) gets sucked into the engine... or look for a non-foam-based replacement which may or may not exist. Assuming I don't find a great replacement, I'd be tempted to fabricate/Frankenstein my own air intake box that fits a standard K&N filter (with comparable or better specs than the Yanmar specified one), which would have a better track record of not falling apart, and which I could easily clean/recharge for the life of the engine. My engine compartment is not particularly (no pun intended) dusty... certainly not compared to what cars have to deal with, so I'm pretty sure a K&N or pretty much anything that didn't fall apart would have no difficulty filtering the air there... Rust/corrosion being the only aspect that comes to mind that's a bit harsher than what I put my car through, Thanks all!

 

[seadaddler]

I have 3YM30 2007 H-36 and I added one of those K&N filter that clamp in place of the factory
air cleaner and I put the factory air cleaner, it was too much noise in the cockpit.
Nick

 

[Don S/V ILLusion]

Curiosity makes me ask - has anyone ever removed an in-tact air filter from their engine and found it to be dirty?

 

[Richard19068]

Curiosity makes me ask - has anyone ever removed an in-tact air filter from their engine and found it to be dirty?

Yes. And I don't have a lot of belt dust.

And I don't know where it comes from but when I shake out the cabin carpets at the end of a weekend or longer trip I always wonder where all the dirt, dust, fuzz, whatever comes from. Just blows in from the island I guess.

 

[Davidasailor26]

Curiosity makes me ask - has anyone ever removed an in-tact air filter from their engine and found it to be dirty?

Mine usually has a small dark area where the airflow is concentrated. Nothing too big, especially compared to the mass of foam that many engines seem to eat.

 

[Benny17441]

These little diesel engines are quite tough, they can chew through that foam and keep on ticking. I think oil fumes and heat breaks up the foam. I replaced one filter and forget how long it lasted, maybe 2-3 years and after that decided just to keep the metal mesh just to prevent larger objects from being sucked in. Don't know why the choice of filtering material. Maybe noise abatement rather than filtering?

 

[Ron20324]

... Don't know why the choice of filtering material. Maybe noise abatement rather than filtering?

I'm not gonna go look it up, but I believe it is called a "silencer" on Yanmars?

 

[Richard19068]

The K&N filter I put on is definitely louder than the stock filter. And yes, the stock one is called a "silencer" by Universal Westerbeke.

 

[Maine Sail]

Curiosity makes me ask - has anyone ever removed an in-tact air filter from their engine and found it to be dirty?

Lots of them.. They are usually filled with belt dust which can contain Kevlar and other damaging fibers.

As can be seen in this photo the K&N filter is loaded with belt dust fibers and is doing a good job at preventing them from being sucked into the intake..

 

[TomY]

Curiosity makes me ask - has anyone ever removed an in-tact air filter from their engine and found it to be dirty?

I have an auto type pleated paper filter fitted to my Nissan diesel. The filter has a metal mesh on the inside and outside of the paper filter.

I can tell when it has become dirty by sooting (unburned fuel due to lack of air) in the exhaust which shows up on the hull.

As a routine, I vacuum the exterior of element right on the engine in the spring. You can see the paper clean up of dirt and belt dust. They last for years with this cleaning.

 

[Don S/V ILLusion]

Lots of them.. They are usually filled with belt dust which can contain Kevlar and other damaging fibers.

Kevlar is actually a very weak fiber when separated from a woven mesh. Regardless, with that exception which typically is caused by uneven belt alignment and wear easily fixed, I’m surprised some claim filters get dirty.