Mercedes 300D Marine Conversion

Discussion in 'DIY Marinizing' started by bigshrimpin, Aug 9, 2006.

  1. bigshrimpin
    Joined: Nov 2004
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    bigshrimpin New Member

    Does anyone know of a kit or shop that will convert one of these 5 cylinder diesels for marine use?

    I have a Volvo AQ130C thats seen better days . . . I'd love to hear if anyone has had sucess putting this motor into a boat.
     
  2. gonzo
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    Location: Milwaukee, WI

    gonzo Senior Member

    Your outdrive is not designed for so much torque. It would be a waste to do the converison to have the drive fail.
     
  3. bigshrimpin
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    bigshrimpin New Member

    I thought the Volvo 270 drives were pretty tough. Some folks have them hooked up to a V8's. The torque curve and HP seems to be on the same line as the Cummins/mercruiser 120
     
  4. Ike
    Joined: Apr 2006
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    Ike Senior Member

    The 300D is a great engine. I drove one for many years. But I doubt anyone would have a kit or do conversions on these. The reason is simply cost. I had my 240D, predecessor to the 300D, (lost compression, needed an overhaul) go in the winter of 1986. The cost of an overhaul was about the same as buying a new engine. The was only a few hundred $ difference. I imagine the cost of converting one of these would be almost as much as buying a marine diesel (which mercedes makes by the way).
     
  5. hartley
    Joined: Feb 2006
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    hartley Junior Member

    mb 300d marine conversion

    An interesting project if ever there was one , a couple of points come to mind
    The 300d ,OM617 engine is rated 77HP at 4000rpm and around 120 ft /lbs of torque at 2400,as you can see it is not blessed with power or torque ,therefore your sterndrive unit will probably cope ,also a firm by the name of Lancing Marine in the UK had a marine conversion kit for this engine ,so it has all been done before ,although probably shaft driven .
    But!!!! taking into account the engineering work involved,and also whether the 300D is a suitable engine is quite another matter ,although these engines ,with the correct coolant will run at 100C and over ,a 10 minute coolant boil will result in a cracked cylinder head or worse ,trust me ...
    The coolant passages in these engines are incredibly small ( quick warm up )
    So all in all,probably not a good way to go , a lot less headaches and easier on the pocket would be to rebuild your present engine .
    How do i know all this ? I own a MB300D and have done so for fifteen years
    But then thats just my opinion ....cheers
     
  6. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    If the torque is only 120ft/lb it won't overstress the drive.
     
  7. larper
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    Location: Sweden

    larper Junior Member

  8. hartley
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    hartley Junior Member

    MB300D marine conversion

    The MB OM617 engines at 125 hp are turbocharged engines ,not naturally aspirated . Good luck.
     
  9. ted655
    Joined: May 2003
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    Location: Butte La Rose, LA.

    ted655 Senior Member

    I have a '78 model 300D. It is in excellent shape. Aside from the cooling doubt, is there any other objection?
    If a keel cool system of adequate+ size was used instead of raw water, would that take care of the marginal cooling issue?
    As far as overhaul costs, I think anything marked "marine" is priced twice as much. Diesels are expensive, period.
    My problem is finding a bellhousing adapter. Mercedes seems to not fit anything.
    The 300 has a reputation as a reliable, tough little engine. The condition mine is in should give me good service for years (recreational use)., BUT.... if there is hidden troubles ahead, here is where I'd like to hear about them. Thanks,:D
     
  10. FAST FRED
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The big question would seem to be how hard will it be working?

    77hp at 4000rpm , not a long life .

    Say 30 hp , 2 gallons of fuel per hour and 2500rpm MAX , it should last well.

    Even better at 1800 and 1,5gph.

    FAST FRED
     
  11. fcfc
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    fcfc Senior Member

  12. ted655
    Joined: May 2003
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    Location: Butte La Rose, LA.

    ted655 Senior Member

    Sadly, I no sprekin de deutz (close?). Yo say habla poko espanoil. My uncle is German but is 4 states away. I'll ask around but here in Cajun country it's doubtful.
    I gather from pictures & the 5 words I managed, that these are conversion/ repair parts foe marinizws Mercedes.
    Thanks for the hard work. I appreciate it!! I'll make it work somehow, FCFC.
    Fast fred; I'm not sure how hard it will work. The purpose of the boat (24' X 8" big Jon) is to push our house barge (50' X 14' plywood hull) from place to place. Somedays would be long ones. Most days it will stay tied & idle. Sometimes with current & sometimes upriver against a 5-8 kt current.
    All this is "slow", we are in no hurry down here. You are where you are at dusk & you tie up & go in da house. Tomorrow is another day.
    So.... I'm thinking a 2:1 reduction gear turning a 20" 3 blade prop running a 2K rpm. IF that gives me the POWER I need to make headway. 2-6kts is plrnty fast for us.
    But... I'm really relying on this forum to tell me what I need as I really know little about gears & props and how to juhhle the 3 components together.
    I am very willing to sacrafice speed for power & longevity. I just wanna push the house around safely, so I'm all ears.
     
  13. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Ted go on the


    http://boatdiesel.com/index.cfm?RED=1B

    Site and pay the $25. They have a calculator that will let you work with different gear ratios and prop sizes . Use 25 hp as the motors output and check with 3-1 gears and a bigger prop for slooo pushin.

    FAST FRED
     
  14. ted655
    Joined: May 2003
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    Location: Butte La Rose, LA.

    ted655 Senior Member

    Good idea, thanks
    Any opinions on transmissions? ZF/Hurth? Twin disk? BW?
    I'm going to need a 10 degree down angle. I don't think everyone makes the dwn agl.
    Hurth does but I've heard they are weak. BUT... what do I know. Any advice?
     

  15. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    Hurth are cheap , so just go a size or two UP for reliability.

    Twin Disc should be available used, "Boats & Harbor?" or a good running takeout.ZF is a ***** for part$.

    The engine may take 10deg down , so a cheaper tranny can be found.

    FAST FRED
     
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