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  1. #1
    Commander drewpster's Avatar
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    Default marinizing smallblock Chevy engine

    I recently came apon a boat that I can have for free if I will haul it off. Regardless of condition I am going to get the boat then decide whether its going to the heap or not. It has a smallblock Chevy 305 engine in it. The current owner explained that he let the factory engine freeze and replaced it with a 305 he had. He mentioned he bought manifolds for it and had the short block rebuilt using a marine cam. The intake and carb are automotive.
    I would like to repower my old cruiser. It currently has a 273 Chrysler inboard so I think the Chevy has enough C.I. to do the job. My question is wether or not it is worth my time and money to completely marinize and build a fresh 305 Chevy engine for my repower. I am considering it simply because I will be getting the complete engine free and regardless of what the previous owner says, I would have to go through the engine before I did anything with it. So my logic is to build me a fresh, properly marinized smallblock out of the free engine or, forget the idea because it would be better to rebuild the already marine. Chrysler. Any advise?

  2. #2
    Honorary Moderator Emeritus tashasdaddy's Avatar
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    Default Re: marinizing smallblock Chevy engine

    not an i/o person, but if it has the marine cam, and he's go the marine manifolds, it's the add on that have to be changed, alternator, carb, fuel pump, ignition. will it mount up to your drive?
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  3. #3
    Admiral KaGee's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Auto carb in a boat is a huge NO-NO!

    There is nothing in a SBC that would bolt up directly to your existing setup. You'll need to investigate what it takes to bolt up your existing driveline to the flywheel and bellhousing of a Chevy block. The manifolds would have to be retrofitted as well. Then there is the issue of the gear ratio, if it is correct for the engine you do install.
    If it were easy, any Caveman could do it.

  4. #4
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    Default Re: marinizing smallblock Chevy engine

    What is the difference between a marine carb and automotive carb??
    1984 - S2 Yachts - 23' Tiara Continential - 260 mercrusier - alpha 1 drive

  5. #5
    Moderator Bondo's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Quote Originally Posted by capecodder116
    What is the difference between a marine carb and automotive carb??
    It's All about how Spilled Gas is dealt with........

    With Marine Carbs,......
    Any Spilled Gas is directed down the Throat of the Carb,......
    Not all over the motor........

    So my logic is to build me a fresh, properly marinized smallblock out of the free engine or, forget the idea because it would be better to rebuild the already marine. Chrysler.
    You're Really Over Thinkng this thing,.........

    The Chevy IS a Marine Engine,....
    Though I don't know about the Peripheral Parts that were bolted to it.....
    Mainly the Carb....

    The Issues you need to be Thinking about are brought up by Kagee,+ to a point, TD.......
    And That's making the Chevy Fit in the Chrysler's place............
    Any Grease is Better,..... Than No Grease at All.......

  6. #6
    Fleet Admiral WillyBWright's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Basically the overflow is directed to the throats so there is no spillage outside of it. They also have a fitting for a hose from the mechanical fuel pump if the diaphragm should fail. On a car fuel pump, the leak would go into the bilge and BOOM. Marine fuel pumps also have double diaphragms.

    Electrical components are made to contain inherent sparks which would also make your boat go BOOM. Car motors are ventilated. Boat motors are enclosed. Leaky car motors leak out of the car. Leaky boat motors leak into the boat.

    Among major internal differences include some to all of the following:
    Forged pistons
    Forged rods
    Forged crank
    Heavier valve stems
    Larger valve guides
    Heavier valve springs
    Roller lifters
    Heavier push rods

    Remember that a car smallblock will rarely see the 4800 RPMs that a marine smallblock is made to run most of it's lifetime. Car smallblocks have a huge longevity problem when put into a boat. Heavy duty truck smallblocks will have far more of the above than a car smallblock.

    Do people put car motors into boats? Yup. But they don't last and they have a multitude of potential sources to blow your boat up with you in it.
    Hey, Have you seen? They make Really Cool life preservers nowadays.
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  7. #7
    Admiral KaGee's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Quote Originally Posted by capecodder116
    What is the difference between a marine carb and automotive carb??
    I can't find my link at the moment. The differences are small, but when it comes to safety, very important.

    It is also illegal. If there were an accident directly related to the use of a non-marine approved carb, starter or alternator, you would have Civil and possibly Criminal liabilities if there were injury, death or other property damage as a result of the unapproved items.

    If it were easy, any Caveman could do it.

  8. #8
    Moderator Bondo's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Among major internal differences include some to all of the following:
    Forged pistons
    Forged rods
    Forged crank
    Heavier valve stems
    Larger valve guides
    Heavier valve springs
    Roller lifters
    Heavier push rods

    Remember that a car smallblock will rarely see the 4800 RPMs that a marine smallblock is made to run most of it's lifetime. Car smallblocks have a huge longevity problem when put into a boat. Heavy duty truck smallblocks will have far more of the above than a car smallblock.
    I'll preface this with,....
    We're talking about Standard Production Marine Engines,.......
    Not the High Preformance motors,....
    Not the Magnum Series,......
    Just the Standard Production Marine Engines,......


    That Said,..........
    Your post is Wrong Willy,........

    The Standard Production Marine engine is the Same as the Standard Production Pickup Truck motors of the same Vintage.........
    Just add Brass Coreplugs,+ it's the Same Motor..........
    Even the cut of the Cam is So Close you'd Never be able to Tell, without a Dial Indicator,+ Degree Wheel......

    From your List,.....
    None of them have Forged Pistons,.. None.....
    All SBC Rods are Forged.........
    None of them have Forged Crankshafts,..... None.....
    Same goes for the valve stems,...valve guides,... valve springs,+ push rods.... All the Same Parts.....
    The Roller Lifters are a Vintage thing,..... When Chevy started putting them in Pickups,..... Merc. started putting them in Boats......
    Any Grease is Better,..... Than No Grease at All.......

  9. #9
    Commander drewpster's Avatar
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    Default Re: marinizing smallblock Chevy engine

    The engine in the free boat I am getting is not a marine engine. It is a standard 305 out of a truck. the previous owner installed it in the boat with new marine exhaust manifolds and a marine cam. (he froze the factory engine and replaced it with the truck 305) I am aware that I would have to get marine induction and ignition and all the do-dads to run the thing. I am aware that I will need a bellhousing to bolt it to my velvet drive (1:1). Based on my conversation with the previous owner, I am sure there will be several items I will have to get.

    Intake, carb, ignition, raw water system, risers to fit my existing exhaust, marine fuel pump, probably a oil pan to fit boat ect....
    You think it is worth it? Or should I just rebuild the Chrysler I already have? I not consider building the Chevy, but It will give me an engine to get ready while I run the Chrysler. It still has allot of life.
    "Your results may vary"

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  10. #10
    Admiral KaGee's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Not telling you what to do, but if it aint broke, don't fix it!
    If it were easy, any Caveman could do it.

  11. #11
    Supreme Mariner Silvertip's Avatar
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    Default Re: marinizing smallblock Chevy engine

    There must be a ton of 318 and 340 Mopar engines out there that would make an easier swap and increase power with far less modification.

  12. #12
    Fleet Admiral WillyBWright's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Bondo, reread. He asked about car smallblocks. My facts are facts. Truck smallblocks have most of what he would need. Car smallblocks would have less. That is what I said. And marine cams aren't just lift and duration, but timing and overlap as well (and probably foremost). My list is more of a "most to all of the above" rather than an "all of the above". It depends on the model. But he has a Chrysler motor anyhow and it's all moot. I have no idea what would be different between Chrysler automotive and marine engine internals.
    Hey, Have you seen? They make Really Cool life preservers nowadays.
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  13. #13
    Admiral KaGee's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Willy my OMC Factory manual Says to see my local Chevy Parts dealer for all of the engine internals.
    If it were easy, any Caveman could do it.

  14. #14
    Commander drewpster's Avatar
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    Default Re: marinizing smallblock Chevy engine

    The previous owner of the free boat I am getting says that marine v8 engines have a higher nickel content.
    Gimmi a break, the BS never stops.
    "Your results may vary"

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  15. #15
    Moderator Bondo's Avatar
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    Default Re: marinizing smallblock Chevy engine

    My facts are facts.
    While your Facts are Facts,......
    The way it's presented Isn't........
    Your post Easily leads to the Rest of the BS that is spouted about Marine Engines,.......

    Just like This BS,.......
    marine v8 engines have a higher nickel content.
    Point Is,.........
    For Rebuild Purposes,..... A Long Block Core motor, Right out of a Car in a Junkyard,.....
    IS in Fact the Perfect Core for a Rebuild..........
    'cause a SBC is a SBC.........

    Btw,.... I know there's More to a Cam Cut than Lift,+ Duration........
    Matter of Fact,....... The LSA is about the Most Critical # to pay attention to when buying a Marine motor's Cam......
    Any Grease is Better,..... Than No Grease at All.......

  16. #16
    Honorary Moderator Emeritus tashasdaddy's Avatar
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    Default Re: marinizing smallblock Chevy engine

    OK, guys the horse is dead, and we still haven't answered the question. he say's he has a truck engine. i think he needs to figure out what it's going to that to mate the engine and drive, plus the required marine add ons. versus, rebuilding existing Mopar, or replacing with bigger Mopar. then total both columns, and the , OH Sh** factor. then make a decision.
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  17. #17
    Admiral tommays's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Is the old motor even standard rotation ?


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  18. #18
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    Default Re: marinizing smallblock Chevy engine

    i just got a rebuild marine engine a few months ago. its at the shop getting put in as we speak. over the winter project?? will take a month or so. a fill in job for the shop its winter here...i asked the same question. the answer i got from most is on gm. truck block and cam and brass freeze plugs. that the main difference...
    but i respect all who post. but about 5 yrs ago i brought a gm. rebuild motor from a gm. parts plus parts place . 350 . 260 house car engine no truck for my buddy who put 10 people in his 22ft. boat . he beat the boat to death for years and ran it 50 mph all the time and motor still run's. we got the motor at the time for 1160.00 no core. now they were 1550.00 or so . these gm motor came with valve covers.timing. and cam covers. but i got mine just longblock no covers.
    bob

  19. #19
    Admiral KaGee's Avatar
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    Default Re: marinizing smallblock Chevy engine

    Quote Originally Posted by Silvertip
    There must be a ton of 318 and 340 Mopar engines out there that would make an easier swap and increase power with far less modification.
    One would think with a little patience you could scout one out.

    If it were easy, any Caveman could do it.

  20. #20
    Commander drewpster's Avatar
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    Default Re: marinizing smallblock Chevy engine

    There is no question I could find a Mopar to do the job. But I seriously doubt it would be free, like the 305. What I will end up with is a start on a marine v8 that I will have to finish, or re-do. Are marine parts for chevy base marine engines cheaper, or , more available? Because while my Chrysler has been a good one, the few parts I have had to get for it have been rather pricey.
    "Your results may vary"

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  21. #21
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    Default Re: marinizing smallblock Chevy engine

    Quote Originally Posted by WillyBWright
    Bondo, reread. He asked about car smallblocks. My facts are facts. Truck smallblocks have most of what he would need. Car smallblocks would have less. That is what I said. And marine cams aren't just lift and duration, but timing and overlap as well (and probably foremost). My list is more of a "most to all of the above" rather than an "all of the above". It depends on the model. But he has a Chrysler motor anyhow and it's all moot. I have no idea what would be different between Chrysler automotive and marine engine internals.
    1 ton truck engines may have the forged crank and exhaust valve rotators with stellite exhaust valves. Cars,1/2 & 3/4 ton trucks are the same other than cams which will be slightly different between cars and trucks.


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