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[Paulus]

This summer by breather tube came loose.  A little oil on the pad below the engine.  I went to the Kubota dealer and he recommended that I replace the fitting and a new tube.  He suggested that I run the top up and towards the back of the engine, instead of down.  Place a small air filter on the end of the tube(K&N as small air filter with fittings on them).  Suggested that I run the hose on a slight grade(up) and by doing this, any condensation from the valve cover will then drain back into the valve cover.  The mechanic at Torresen does not recommend sending it into the air filter.   Would appreciate any thoughts on this subject.
Thanks,
Paul
We have returned from the North Channel after 10 weeks and this was my only issue.

[Ron Hill]

Paul : In my M25XP engine here's what I did for about 23 years:

I made a circular foam filter that fit inside a leaf guard for a downspout.  I put a bottom 1/4 od a beer can inside so the foam fit and had a hole on the foam so the vent hose went inside. 
You'd be surprised how much oil vapor condensation my home made critter caught!  I'd wash it out with every oil change and reinstall it!!

Westerbeke recommends that you take that vent hose and vent it to the air filter (I wrote a Mainsheet tech note article in the mid 90's on that topic).  You can also (number of C34 owners have done it) drill and tap a fitting in the air intake manifold and attach the vent hos eto the fitting.
this has been written up a number of times on this board and should be in WiKi .

A few thoughts

[Paulus]

Thanks Ron, the first method is how I have been dealing with it.  Just thought I would try something different and the idea came from the Kubota dealer.  The mechanic at Torresen did not recommend it going back into the air intake.
Paul

[Steve W10]

Hey Paul, 10 weeks and that's the only problem, awesome, gotta love a well-maintained Catalina!

I wracked my brain on the same issue for a long time, read everything I could, really wanted to rid my cabin of any diesel or exhaust odours.  Here was my thought process….

Option 1 - Hooking something up to the air filter as others have done, but I preferred something I didn’t have to deal with every time I serviced my K&N.

Option 2 - Again like others, planned to put an oil separator in line from that breather to a fitting I’d tap into the intake manifold.
My biggest concern was that I’d create a slight vacuum in the crankcase and I wasn’t totally sure what ramifications that would have.
Figured I could decrease the vacuum by soldering shut one of the fittings and then drill a small hole into that solder - nice little orifice.
Then to test it, I was even going to put a “t” in the system for a vacuum gauge to measure it all at different RPM, then increase the size of the hole as required to get the best average performance.

I thought I was really clever, bought all the stuff and when I pulled the manifold off I found the area I wanted to tap was very thin, something like 1 mm.  I decided that was too thin to reliably hold that fitting; it may only be one or two rows of threads.  I’d like to know where others have tapped?

Option 3 – Out of frustration I just took the 3’ of hose and ran it down into my blower intake (near the packing gland).  Until I revisit this thing I just run the blower whenever my diesel is on.  Because it’s not a tight fit (3/8” into 3”) I don’t think it’s creating any vacuum.  I don’t think this is a really good long-term solution and certainly in time that drier hose to my blower will get some oil residue, but so far (after one year) it’s not too bad.  Definitely no exhaust smell in the cabin at all.

Aside: One possibility in options 1 and 2 is to put a fastener (bolt) inside the air filter or manifold using an NPS vice NPT fitting of course.  I’m too paranoid it could fall off and get ingested into the engine.  Also obstructing the airflow in the manifold won’t help performance any.

Sooooo…. I’m still looking for the best solution too.

Steve

[Ron Hill]

Guys : There is also another solution that has bee on this message board before and I've also read about it in magazines. 

It's really made for very large engines.  It takes the condensed oil from the vapor and feeds it back in to the oil system. 

[cmainprize]

this was our solution about four years ago and has worked well, no oil residue our engine issues so far.  the picture does not show it well but the line from the separator goes into the k&N air filter.

[Footloose]

Why does one have to use an oil separator?  Couldn't one just let the oil get sucked into the intake and be burned in the cylinders?

[Indian Falls]

Good question!  I ran my hose direct to the air cleaner/strainer.  Works fine, no smell.  I don't find pools of oil in the low spots of the hose.  The vent emits a bit of smoky vapor that is sucked back into the engine.  I see no reason to put your hose in a pop can with diapers unless you like the smell of crankcase fumes nor do I see any reason to strain oil droplets suspended in air from what goes into the engine.  But, that's just me...

[cmainprize]

After 4 seasons I would agree the separator is not mandatory, I was never really sure how much oil was going to come out of the hose so I put the separator in.  I empty it once a year and it is around 1/3 full.  We motor around 30-40 hours per year.  I would suspect  some engines may vent more or less oil depending on the condition of the engine.  The couple of ounces of oil I drain could easy be consumed by the engine with no issues, but I don't regret putting in the separator.

[Brent Evans]

I've run a hose into my air filter for the last 3 years with no problems. . . until last week.  I've got what I think was the original air filter on my 86; a simple foam filter wrapped around the intake with a round metal housing to hold it all.  Then on a beautiful Sunday afternoon with friends aboard we started to go out for a sail and the blankety-blank engine wouldn't start. This was a first.  My engine has never not started.  I was dismayed and puzzled but being in my best white khakis I wasn't going to start any repairs or investigation then, so we ended up drinking margaritas at the dock.  Had a very nice time all and all.   

Still, first chance I got I went back to the boat to see what I could find out.  An old diesel mechanic had told me that a diesel engine will run forever if it has 3 things: compression, air and fuel.  So I started with that.  I knew I had compression; the engine was turning over as normal; not too fast or too slow.  I checked the kill switch and made sure that was fully in the off position on the engine.  What next?  air? fuel?  I was gearing up to start bleeding lines, changing fuel filters etc. when I thought, "what about the air?  Surely that's not it!"  I removed the center nut holding on the top of the air filter and pulled off the filter and tried to start the engine.  It started immediately!  The old girl wasn't getting enough air!  Over time, the filter had become saturated with enough oil to restrict the air getting into the engine!  Shame on me for not cleaning it for the last 2 years!  This will not happen again!  That's one filter I'll clean on a regular basis, believe me!

[Indian Falls]

Brent, You have something different than the aluminum shavings packed into your air strainer? 
Mine is no "air filter", it's only intent is to keep large objects out of the intake.
Mine may have had a foam band around the outside but that is long gone.  Whenever I've looked at my strainer it's a bit oily but nothing but grease would restrict air flow through this thing.  My breather hose goes directly to the cover and any oil contained in the flow out of this hose will keep my aluminum shavings well oiled to catch dust I suppose.  It certainly is not dripping with oil. 
Keep in mind... people will tell you not to do something because they really don't know what the result will be... in this way they keep their ass covered by telling you not to.  Just use common sense.

[Brent Evans]

Thank you, Dan.  Perhaps I should see how others have upgraded their intake "filters" (such as they are) to a more modern and protective one.  I have a very early boat (1986, hull #38) which may need upgrading.  Maybe Stu and others of this vintage can advise how best to do this.

[Ron Hill]

Brent : The only difference between your 1986 (and the 1987 is/was the same) is that your external cover has a "snoot" on it, whereas the others - 1988 thru 2009 have a round external air filter with a foam "noise suppressor" around the outside!!

A thought

[Stu Jackson]

Thank you, Dan.  Perhaps I should see how others have upgraded their intake "filters" (such as they are) to a more modern and protective one.  I have a very early boat (1986, hull #38) which may need upgrading.  Maybe Stu and others of this vintage can advise how best to do this.

Brent,

Like everything in boating, there is no "Best."  Everything is an OPTION.  Those options have been discussed in this post and many in the C34 Tech wiki.

I have chosen to use a modified version of Ron Hill's "beer can" but I used a "peanut butter" jar with a hole in the top for the hose and multiple other holes for venting.  I did this primarily because I could never get the elbow connection to the engine to move and I didn't want to break anything.

Others, like Steve W described, have routed their crankcase vents to the air intake, with many different ideas as to whether or not to just hang it on the intake or to drill & tap and to make a positive connection.  Whether you use a K&N filter or use the newer version of the air take "filter" with the foam cover, is your choice.

If you look at the engine manuals or the Torreson website (www.marinedieseldirect.com), you might see the "old" and "new" (1986???) air filters.

This is NOT rocket science, and only has a few options.

Your boat, your choice.  

Sorry if I'm a bit cranky today, I'm still wrestling with my darned galley sink drains.  Hadda buy a Dremel tool to get the danged plastic nuts off.  Yeah, I used to have an early Dremel tool, but its motor bit the dust like many of the earlier models.  Lets hope this puppy lasts longer.