So... What exactly is the difference??
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So... What exactly is the difference??

  1. #1

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    Default So... What exactly is the difference??

    OK guys,
    You have all helped me alot with my questions. So here is one to show you just how much I don't know.

    What exactly is the difference between a regular motor and a marine motor? I want to pull the 350 out of my boat and put a 454 in it. I'm looking at this old suburban of mine, and thinking that I should just pull the motor, build it, and drop it in the boat.

    What are your thoughts??

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  3. #2
    Senior Member Fonz69's Avatar
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    I am by no means an expert on this but they are physically the same

    Remember a jet or boat motor sees a constant load unlike your Suburban that has a transmission and can do highway speeds at a low rpm

    In a boat motor you have to watch out for things like reversion of the water in the exhaust getting sucked into the heads and allowing more piston sidewall clearance for high long rpm runs in a jet boat.

    Also a larger oil pan and changes in the heads in regards to the oil building up on the heads and not returning to the pan during long high rpm runs

    But all things said if you take it easy and use the boat for cruising and ski/tubing I have seen transplant motors last a long time.


    Best investment in my opinion is at least bolt on a larger capacity oil pan

  4. #3
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    In my humble opinion ...the short answer is HELLZ YA. Get a 12 pack and a cherry picker and get to it. This Sunday I was just at the lake with a buddy's boat who did the exact same thing. His boat GPS'ed 59.5 mph with a box stock 454 in a 19' Bahner jet with a 650 Holley carb. Not too bad

    The long answer is...
    • gererally tighter bearing clearnces on an automobile engine compared to a marine engine.
    • Jet boats create a large engine load and oil temps, need slightly looser clearences.
    • Small oil capacity /pan. 300 degree oil temps on a long cruise with 6 quart car/truck pan are possible.
    • Oil filter bypass spring has a low pressure spring. Marine units are a heavier spring or bypassed all together.
    • OEM car cams built for 2000 rpm cruise with 4000k max.
    • Weak valve springs will tend to float at jet boat cruise rpms. (3500-4500 rpm)
    • Typically crappy timing chains prone to failure.
    I'm sure there are a few things I'm forgetting but you get the idea. It will work but may have a short life if you pound it on a regular basis. If you go easy on it you could be rocking for a few seasons...never know.

    Good luck with the project.

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  6. #4
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    Ya beat me to it. I took to long typing but you get the idea.

  7. #5
    Senior Member Brendellajet's Avatar
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    Piston to cylinder clearances are also slightly different. In a jet boat, the block generally stays very cool, while the rotating assembly works very hard.
    "He is a lover, not a fighter. But he's also a fighter, so dont get any ideas."

  8. #6
    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by Tras_h View Post
    OK guys,
    You have all helped me alot with my questions. So here is one to show you just how much I don't know.

    What exactly is the difference between a regular motor and a marine motor? I want to pull the 350 out of my boat and put a 454 in it. I'm looking at this old suburban of mine, and thinking that I should just pull the motor, build it, and drop it in the boat.

    What are your thoughts??
    Pretty much the brass freeze plugs and the USCG "Marine" acessories (fuel pump, alternator,starter, carb, distributor (fuel handling and spark-making elec. systems))

    Larger oil reservoirs are comon, but by no means mandatory for the use.
    I wonder sometimes how many people's "Cove Racers" are out there with 10, 12, 14 qt oil pans on, that will NEVER see a WOT run over a 1/2 mile, let alone the 4 and 5 mile ones I do, with a 5-qt pan and 2-qt filter, along with all day skiing & tube pulling.

    Internal clearance specificatiomns are the same, normally using the "performance" specs, which are the wide 1/2 end of the factory clearance ranges.

    The hard parts are all the same as automotive engines.

    My stock chevy valve train wouldn't float untill 6-grand (did this once cavitating trying to dodge a jet-ski set on "blind ram").
    Float @ 3500-4500 = BS.

    Equate a "marine" engine to "truck" engine, not "car", and you will be closer to the mark. More RPM used, but the same needs for good strong torque production low, keeping it pulling in the midrange, and then not starving it at the desired peak RPM.
    Jets will let you get away with a few things in the low and middle areas, due to it's differnt power utilization demands than a prop, but only so much.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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  9. #7
    Senior Member Jetboat Jared's Avatar
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    im running a bone stock 427 bbc tall deck and i havent had any problems. runs great it keeps up with my uncles blown small block 350 boat lol

  10. #8
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    The cam shaft has a bunch to do with it. If you look at were the HP and torque curves are. You would want to change it out, rebuild or not. Might as well add some roller rockers while you're into that part of the motor, better push rods. Screw it, get some good aluminum heads and intake. But then you could build the 350 to a 383 and some bolt on goodies and make more power than that old stock 454. That would be the easest thing to do. Build it the same as this one.

    http://www.jegs.com/p/GM+Performance/749878/10002/-1

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