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  1. #1
    Seaman Apprentice NateL's Avatar
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    Default Can you convert any engine into a marine engine?

    Just curious for later reference. If so waht does it take to do so?

  2. #2

    Default Re: Can you convert any engine into a marine engine?

    In the early years when boating became a general pastime and before dedicated marine engines were available, it was common practise to marinise auto engines. At the very least you need a marine alternator, water cooled exhaust box and water intake and exit for engine cooling.

  3. #3
    Moderator Bondo's Avatar
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    Default Re: Can you convert any engine into a marine engine?

    Can you convert any engine into a marine engine?
    Ayuh,.... Unless you've got a Full Machine Shop,+ a boatload of knowledge,....

    Nope....
    Any Grease is Better,..... Than No Grease at All.......

  4. #4
    Chief Petty Officer LX Kid's Avatar
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    Default Re: Can you convert any engine into a marine engine?

    Seems feasable to me. Bronze freeze plugs, marine water pump, marine oil dip stick, marine alternator and bolt on cooling system of your choice. (Sea water or closed system)
    1982 Grady White 241 Weekender, Outdrive Pre-Alpha, GM 305 V8 Engine Model 228 w/Edelbrock 1409 Carb. Bought 9/1/08 (Took 2 years to get it lauched)

  5. #5
    Moderator Bob_VT's Avatar
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    Default Re: Can you convert any engine into a marine engine?

    Cooling system
    Freeze plugs
    Cam change
    ALL electrical parts
    Fuel Pump
    Carb or fuel injection

    If you are going to select a motor that is not normally used for marine work...... then add in all drive components.

    It is not worth the money
    This is a great link to boat specifications http://boatspecs.iboats.com/
    Please, shop iboats first!!


  6. #6
    Chief Petty Officer
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    Default Re: Can you convert any engine into a marine engine?

    If the engine is to be freshwater/glycol cooled why would you need to change the freeze plugs? (assuming you give the block several coats of paint on the outside)
    '77 Luhrs 28', had GM diesel V8 last year, now installing Mercruiser 5.7 gasser w/ 310HP!!

  7. #7
    Chief Petty Officer
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    Default Re: Can you convert any engine into a marine engine?

    A new Chrysler Pentastar V6 engine with no exhaust manifold (casted into cylider head). No need for a wet exhaust. A good candidate for marinization.

  8. #8
    Petty Officer 2nd Class
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    Default Re: Can you convert any engine into a marine engine?

    Yeah, it ends up you can use the block (if you change the freeze plugs), the cylinders, the crank (usually), most of the head, lifters/rods, but not a whole lot else. Many boat engines started out as truck engines but the unique environment needs a lot of changes:

    Shielding: Truck engines drop gas fumes out the bottom of the engine compartment, which is just outside air. The heavy fumes can't drop out the bottom of a boat, so it collects in the bilge in a cloud. Even when using the blowers, there might be some fumes around puffing out from time to time. That means everything electrical -- starter, alternator, various pumps, etc -- has to be shielded, usually with a fine metal screen, to keep sparks from escaping. The air intake above the carb is also shielded to prevent a potential backfire from igniting these fumes.

    Pitch and Roll: Trucks may climb hills, but not like the sides of waves that boats take. The oil pan and pump have to be deeper so that the oil pump head is always submerged even if the boat is temporarily mostly sideways.

    Power: Trucks and cars tend to like to run around 2000ish RPM -- transmissions can ease the truck up to speed, then drop into a lower RPM for cruising. Inboards like it around 3000ish RPM. The camshaft has to be different so that power/torque and fuel efficiency are geared toward the higher RPMs.

    Cooling: The water pump on a truck is on the block. On an I/O it's on the outdrive, and the block holds a circulator. The exhaust system is cooled with water-jackets. Brass plugs aren't entirely necessary with a fresh-water cooled engine, but an engine compartment is a hostile environment, and if I operated in salt water, I'd be worried about paint eventually knicking off the plug and salt air corroding the steel.

    It's cheaper and much less of a hassle to go with the marine engine, but I've read about a few people doing a conversion just for the fun of it. I've seen a few doing a Google search when I was looking for auto vs marine parts when I was overhauling my 3.0L.

  9. #9
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    Default Re: Can you convert any engine into a marine engine?


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