Engine Rebuild
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Engine Rebuild

  1. #1

    Join Date
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    Default Engine Rebuild

    I don't know too much about rebuilding marine engines. I have experience in rebuilding diesle engines for trucks and I am currently getting into building up performance engines for mud trucks and muscle cars. My Dad however has a boat with a Murcury 502 in it and he is wanting to rebuild it. I have looked up stroker kits, cams, heads, and other parts for the 502 but I have no idea if they would work for a boat, seeing that boats unlike a mud truck or street rod stay at a constant RPM and obviously have to keep the fact that they are in water. Basically would any good engine performance parts work with a 502 in a boat from any regular performance dealer or do I have to find marine specific parts? Any help is greatly appreciated, thank you.
    Last edited by BigMo; 02-09-2009 at 03:00 PM.

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  3. #2

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    On this topic you will get mixed reviews. I would suggest going with marine application parts such as cam, heads, etc. But you will have others tell you they bought a GMPP 502 and stuck it in there and has been running great for a few seasons. When picking out cams you also need to worry about revision and all that. Im no guru and not trying to be so I will now stop and let someone with all the info chime in.

  4. #3
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    Just remember with most marine applications you have fixed gearing so the engine has to run from idle to wide open throttle.

    The 502 is in what type of boat? Jet/V drive/I-O?

    How much power is your dad wanting? or better yet how much faster does he want to go?
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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  6. #4
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    If that boat has an out drive, you'll want to keep the top rpm to about 5200. You'll also want an idle friendly cam as those drives don't like to be bangged into gear. Most performance parts will work. The bearing clearances are a little bigger and the cam sellection are the main differences in the build. Thats my .02 worth. Now for some one else to put in theirs.

    Tim

  7. #5
    Super Moderator HammerDown's Avatar
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    Mo, you'll get great advice from some very knowledgeable people here...
    <img src=http://www.performanceboats.com/gallery/data/500/medium/06-30-11_1234.jpg border=0 alt= />

  8. #6
    Member bennyb's Avatar
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    Mo, welcome to PB
    20'5 Advantage classic cruiser
    Go on get your ass outa here

  9. #7

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    Quote Originally Posted by cstraub View Post
    Just remember with most marine applications you have fixed gearing so the engine has to run from idle to wide open throttle.

    The 502 is in what type of boat? Jet/V drive/I-O?

    How much power is your dad wanting? or better yet how much faster does he want to go?
    He says it is an I-O and he would eather like to add a little more horse power to it or just do a stock rebuild depending on how much money its going to be for eather one. The engine is sitting in a 1995 29' Scarab. I dont know if that makes a difference as far as the size and weight of the boat or not.

  10. #8

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    Quote Originally Posted by Eliminator Cruiser View Post
    Mo, welcome to PB
    Thanks.

  11. #9
    1976 Sanger Flattie Running_on_Empty's Avatar
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    most differences from automotive to marine are bolt on parts that must meet coast gaurd approved rules. Distributor, fuel pump, carberuator, starter, and spark arrestors.

    Other things are corrosion resistant things like, for example, brass freeze plugs.

    Another thing to consider is running temp....if you run the boat in salt water....salt water crystalizes at around 170 degrees

    Cam selection is important.

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