I have a M25 that has a 90 degree hose nipple coming off the side of the valve cover. No hose is attached. You can feel a little pressure of air/gas being pushed out while the engine is running. My next door Cat 30 owner's M25 has a hose attached that runs down below the engine. I have seen a picture online of an M25 that has a hose attached that then runs to the top of the air filter. Bought mine used about 22 years ago and it has never had a hose attached. Rebuilt the engine 10 years ago and didn't notice it till a friend pointed it out last week. Is it a breather hose that I need or just leave it as is?
Question on M25 vent hose off of the valve cover
- Thread starter Ed Childress
- Start date
It is the crankcase breather outlet, best to have a hose that runs to your air cleaner, keeps smells out of the boat. There's lot's of information about this in the forum, here's just one thread:
1989 M25XP PCV Question
So my boat has previously had the PCV run directly into the intake I can tell because there was a ton of oil in the original air cleaner that I replaced with a K&N. I didn't know why it was covered in oil at the time but I tried to clean that up and I put on the K&N. So anyway then the owners...
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Breather Hose 101 (w/ K&N Filter Pictures from Rick Allen)
K&N air filter breather hose
and Noah's: Oil "breather" hose to Air intake
and Kloeber's PDF and wiki link: Options to route crankcase breather to air intake
Engines 101 - The BIGGEST & BEST collection of M25 Series Universal Engine Information on the Internet, plus some M35, too
Diesel Engine - c34.org
K&N air filter breather hose
and Noah's: Oil "breather" hose to Air intake
and Kloeber's PDF and wiki link: Options to route crankcase breather to air intake
Engines 101 - The BIGGEST & BEST collection of M25 Series Universal Engine Information on the Internet, plus some M35, too
Diesel Engine - c34.org
