Yanmar 4JH-TE exaust system sizing

Discussion in 'Diesel Engines' started by KnottyBuoyz, Nov 9, 2009.

  1. KnottyBuoyz
    Joined: Jul 2006
    Posts: 829
    Likes: 56, Points: 0, Legacy Rep: 685
    Location: Iroquois, Ontario

    KnottyBuoyz Provocateur & Raconteur

    Question. I have a Yanmar 4JH-TE. Exhaust outlet from mixing elbow is 3" Dia. The muffler and exhaust hose that came with the engine has inlet/outlet size of 1-5/8". Somewhere along the line there must have been a reducer of some sort but that wasn't included. I have the service manual for the engine but there's no mention of minimum exhaust size requirements. I don't know much about diesel engines, well actually at this point I know nothing about them, but if they breath better, larger exhaust, they should run better no? Can I go down to 2" all the way back (approx 12' run through water lock, muffler & gooseneck)? That should be better for the engine or should I keep it 3" all the way back?
     
  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    2 inch seems good to me, assuming that it is an almost straight tube gently sloping down to the muffler. How do you plan to connect it to the 3" exhaust?
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Get an installation manual for the engine. You can probably download it. It has everything you need to know.
     
  4. Frosty

    Frosty Previous Member

    I do have the Yanmar installation manual and the rule is never ever go less than the engine outlet. This is a turbo engine and 2 inch is ridiculously small, if its a power boat use nothing as a silencer or dump bucket.

    I have the 6Lp and use 100 mm all the way out. Its not noisy being turbo.
     

  5. KnottyBuoyz
    Joined: Jul 2006
    Posts: 829
    Likes: 56, Points: 0, Legacy Rep: 685
    Location: Iroquois, Ontario

    KnottyBuoyz Provocateur & Raconteur

    Thnx Fella's. I have the service manual but it says nothing about exhaust hose dia. or back pressure etc.. Since I have to buy all new exhaust components anyways I'm going to go all 3". I don't know exactly where the smaller muffler & hose came from but I'm doubting it was with this engine.
     
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