Boat motor conversion

Discussion in 'Gas Engines' started by Vettmech, Jun 13, 2009.

  1. Vettmech
    Joined: Jun 2009
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    Vettmech Junior Member

    I see alot of talk posts about using auto engines in boats but can I convert a 350 4 bolt vortec boat engine to be used in a car. ????
    Thanks
     
  2. PAR
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    PAR Yacht Designer/Builder

    Yes, the standard marine conversion and one of the most popular engines in use.
     
  3. CDK
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    CDK retired engineer

    Not that it's done often, but you could.
    You will run into tiny problems, like finding an exhaust that can be bolted to the manifold, a carb with an accelerator pump and coolant hoses to and from the radiator and heater. And a clutch instead of the engine coupler would also come in handy (not reqd if you use an automatic gearbox).
     
  4. Vettmech
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    Vettmech Junior Member

    I got it at a very resonable price ...has a bad rod bearing didnt turn it but it did lack oil and screeched it. Well Im going to try it because its a GM Vortec engine per the Block Casting number. The heads I dont know about (no GM casting numbers) but they resemble the L31 head in regards to the screw in rocker studs has a DRT 007 and SS and in the middle theres a rounded triangle with an M in the middle where most trademark logos are located. Im hoping they have the Vortec heart shaped combustion chamber.. wont know till I pull them.

    Im sure standard exhaust manifolds or headers will bolt right on. And as far as carb is concern Edlebrock makes a perfomer intake for the Vortec. Someplace I read the cranks in the boat engines are forged not cast another plus. And rods are nodular with an oil channel foir piston cooling another plus.
    So may pluses... Cam and springs will be changed for my street specs.

    Thanks alot for the info so far...
     
  5. Ike
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    Ike Senior Member

    The GM engine you are talking about is pretty standard in boats and autos, I have one in my motorhome. It may have a different cam due to differenct loading in a boat vs a auto. but it should work.

    By the way, for many years Corvette's were built with an engine by Mercury marine. So it works both ways if you know the slight differences.
     
  6. PAR
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    PAR Yacht Designer/Builder

    Unless the engine is to live wide open (not enclosed in a box of any kind) then you'll have to use a wet exhaust.

    All the parts for the conversion are available. You will need a cam, transmission, jet or outdrive, and a number of assorted other things, like a shielded alternator and starter. Exhaust manifolds will run $130 each, plus risers, etc.. They'll fit a 305, 350 or 377. A exhaust kit will run about 600 (and up). A 55 amp alternator is about $150. A starter about the same.

    There are quite few details involved in this sort of conversion. It's fairly easy, if this isn't your first time "around the block", but can drive you nuts tracking stuff down if you're a novice.

    If you are new to this, you may be better off buying a spent setup and swapping out the long block for the Vortec. This way you'll get the manifolds, raw water pump (not the same as the circulation pump) and other related equipment.

    Before you start bolting on intakes and other speed equipment, you need to understand that most pleasure boats don't respond to "Hot Rodding" like cars do. You can double the HP of your bow rider (for example) and only get 5 more MPH top speed and half the fuel mileage it got before.

    What kind of boat are you dropping this 4 bolt main into?
     
  7. Vettmech
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    Vettmech Junior Member

    PAR you have it backwards Im considering putting a boat engine in a car not a car engine in a boat... read my first post. I couldnt use an outdrive in a Corvette...unless it was anphibian (spelling)

    Im going to salvage the good parts out of a boat engine and put them in a Vette.... like the 4 bolt block crank and rods ...the rest can be High performance equipment. Im getting positive info from this thread that I can do this and have a very durable impressive street machine. With the right heads 400 to 500 hp should be attainable with the roller block.

    Thats my thinking... do you think Im on the right track?
     
  8. PAR
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    PAR Yacht Designer/Builder

    Yep, all the factory and aftermarket equipment will bolt directly to the block.
     
  9. rcig
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    rcig Junior Member

    don't forget to change all freeze out plugs to brass and use marine head gaskets. automotive in marine environment will deteriorate and eventually leak. head gasket will let water in and blow the engine.
     
  10. Vettmech
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    Vettmech Junior Member

    Im not using marine gaskets!!!! LOL Im putting a boat engine in a car
     
  11. marshmat
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    marshmat Senior Member

    Not everyone reads the whole thread ;)

    The marine environment is somewhat more demanding than a car engine normally experiences, so modifying a marine Vortec for car use ought to be easier than doing it the other way around. The boat version has a different cam, of course, and different accessories. But it's still essentially the same engine. There are some marinizers who put beefier internals in, since a boat motor sees as much WOT use in a day or two as the average car sees in its lifetime. If this is the case with yours, putting it in a car would yield something nearly bulletproof.

    The downside, of course, is that more often than not, a boat engine is heavier and more expensive than a high-tech car engine of comparable peak power. But in your case, it's the same basic block, and you're planning to swap cams, tweak the heads, etc. anyway.

    Budget a few thousand extra for several sets of rear tires....
     

  12. Vettmech
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    Vettmech Junior Member

    Thanks MAT
    I am going to select a new cam... and as you say tweak the heads.
    The GM Bowtie blocks are heavier to, but for a good reason..to keep the block from flexing at high RPMs. They are nearly bullet proof also. The front and back walls of the block are nearly an inch thick. end main bearing bosses are much heavier too. Some guys are using block fill in the auto blocks in the lower portion of the water jackets to strengthen and control block flex. At 7 grand a regular block can flex up to a 1/16 of an inch.

    This boat block is heavier for sure. Thanks Mat
     
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