How about a basic overview for the newbie :-)

Discussion in 'DIY Marinizing' started by jeffb957, May 25, 2014.

  1. jeffb957
    Joined: Dec 2013
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    Location: Huntsville, Alabama

    jeffb957 Junior Member

    Hello all.
    I have been helping a friend recover from an unexpectedly cold winter, and insuficciant winterization. Cracked heads, block, and exhaust manifolds on a 5.7 liter Mercruiser IO. From that I have seen what a wet manifold is, and I've seen the flywheel and bellhousing differances. I've seen that the water pump is very different. There also seems to be a lot of safety gear on the fuel pump and lines, as well as the flame arrester on the carb.
    From that, it seems to me that if we got ahold of one of the old late 80's GM diesel engines that were based on the small block GM engine, and bolted up the marine accessories, we'd have an easy diesel swap. Of course the fuel system would need a good clean-out, and we'd probably need to change props to account for a little higher torque and a little lower RPM. am I missing anything here?
    If the GM diesel idea doesn't work, can you give me a thunbnail sketch of the marinizing process?
    Thanks
     
  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Olds fooled around with a 350 based diesel (DX block). It was one of the worst engines ever built and wasn't produced for long.

    You could swap in a diesel, though the O/O gears would probably need to be changed and possible several other parts to handle the bigger torque figures, typically produced by them. There will be several other considerations on a swap like this, so pick your poison.

    You'd be best advised to go down to the local bone yard and pick up a first gen small block and swap out the parts. There are 3 versions of the first gen: the large journal, the small journal (flanged crank) and the one piece main (LT). The LT block is the one you want and there are millions of them. They weren't produced for long, but they are undoubtedly the best of all the small blocks. Starting in the early 90's they where used in trucks and cars. By '96 or so they stopped in cars, but continued in trucks. They're easily identified as not having a fuel pump provision on the left side of the block. They also have a one piece rear main seal, which was always an oil leak, on the earlier version two piece seals. The LT heads are the best and flow better than most aftermarket heads. If you can't get one of these, get the small journal block, which was produced from 1968 to 1990. These have the fuel pump hole and the leaky two piece rear main seal.

    You'll need new manifolds, but everything else should just swap over, saving a lot of headake and parts searching/fabrication. Swap out the cam, intake, carb, distributor, alternator, starter and other marine equipment and go boating quickly and relatively cheaply.
     
  3. jeffb957
    Joined: Dec 2013
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    Location: Huntsville, Alabama

    jeffb957 Junior Member

    Yes, now that you mention it, the 350 based diesel I was thinking about was in an Olds. It belonged to an old lady up the street when I was a kid. I made extra money waxing her car, and doing oil changes for her a few times a year. she never had any trouble out of it, but she drove like a little old lady :D
     
  4. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I have a few old lady friends and they all have cars only a person like me can dream about. Gloria is an example, 74 and spunky as hell, but her 6 year old VW Pissonit has less then 17k miles and is like new. I occasionally get them to sell, so they have cash for a new one. Her last one had 30k on a 11 year old car. The dealer was trying to tell her it wasn't worth anything, but I sold it at top dollar to a guy looking for nice car, to send his daughter to collage in. She had thousands to put down on her Passat. Trust me the small diesel variant didn't do well and had a justified quick death.
     
  5. daiquiri
    Joined: May 2004
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    Location: Italy (Garda Lake) and Croatia (Istria)

    daiquiri Engineering and Design

    That's the mileage I make in one year... :eek: The oil industry owes me a big thanks for all the money I am pouring into their pockets. :D :eek:
     

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

    FAST FRED Senior Member

    Olds fooled around with a 350 based diesel (DX block). It was one of the worst engines ever built and wasn't produced for long.

    Indeed the FIRST ones sucked they were modified gas car engines.

    GM finally cast a far better diesel block and crank with different bolting that is the dream of the car racing set. 7500rpm with mostly stock parts (and a good balance job) .

    A bit of hot rod looking should find the correct casting # to look for .

    The Diesel cruise RPM will be lower than a stock gas car engine , so you would have to love the boats performance at 2500 -3000 rpm , a diesel 4500-5000 as with a gas car would be too difficult .
     
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