Connecting breather hose directly to intake silencer inlet in M25-XPB

Mar 6, 2008
316
Catalina 310 Scott Creek, VA
I have been reviewing posts about replacing the intake silencer with a K&N filter. Some have also connected the breather to the K&N. There seems to be no consensus on if this is a good idea or not, however in reply #2 to this post https://forums.sailboatowners.com/index.php?threads/k-and-n-air-filter.157234/#post-1067120 Jessie says he tried it and decided to disconnect. Where should I route the breather line if I go with the K&N but do not connect the two together? The existing hose is 5/8" ID and very flexible. What type of hose is used for this application?
 
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
Yes, I disconnected it. I was watching my oil level. Each time I started the motor and found I was gaining oil. I couldn't really come up with a true mechanism as to why this was happening. I disconnected and have the end of the hose about 1 inch from the filter. Works fine.
 
Sep 29, 2008
1,865
Catalina 310 #185 Quantico
I still have my breather hose attached to my K&N but in between I added a fuel/water separator. I do not get the oil build up on my air filter and my crankcase is ventilated.
 

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May 20, 2016
2,992
Catalina 36 MK1 94 Everett, WA
K&N even sells an adapter to connect a breather hose to the filter, I also have an oil separator on the hose to prevent an oily filter.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
K&N filters are designed to be oiled, it is how they capture debris. If you have a dry K&N it isn’t doing its job. They have no magic capability to make crankcase oil. I simply installed a brass nipple into the rubber end plate of the filter and pushed the breather hose onto the filter. Works great.
 
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
They have no magic capability to make crankcase oil.
The only thing I could figure was it was creating too much suction on the breather tube and pulling some fuel past the cylinders but that was a long shot. I couldn't really explain my observations.
 

Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
I have worked on diesels that take an amazing amount of time for oil that is added to the fill to make it down to the pan. As a result I ended up with too much oil in the engine because I overfilled it.
 
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Jan 30, 2012
1,091
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Jessie

Your breather is not the culprit here. Do you have an engine driven lift pump? If so - and if the diaphragm leaks - your oil level will rise. It is possible an injector might leak down ovenight but the quantity would be quite low.

Charles
 
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Nov 18, 2010
2,441
Catalina 310 Hingham, MA
Jessie

Your breather is not the culprit here. Do you have an engine driven lift pump? If so - and if the diaphragm leaks - your oil level will rise. It is possible an injector might leak down ovenight but the quantity would be quite low.

Charles
I would agree but it doesn't change the fact that the oil stopped increasing after I disconnected the breather tube. And this was something I monitored for over a month.