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  1. #1
    Cadet
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    Default Replacement OMC 5.8 351W

    Howdy,About 3 years ago, I bought a 90 Chris Craft. It has an OMC 5.8l 351 in it. After running it for 1 summer, I started getting water in the oil. To make a very long story short, I pulled the engine and found a crack in the bottom side of the block about 16 inches long. Now, I am looking for either a used engine to rebuild myself or an already remaned engine to just drop in.I have a few questions for you pros.1. Can I find an old 351 from a junk yard or an old Ford van and pull that, rebuild it and drop it in my boat with no problems?2. Should I be looking for a marine engine for this boat?3. If so, why would the marine engine be better?4. Does the cam have to be a certain degree to stay away from reversion?Now keep in mind, I want to get back on the water for as little money out of pocket as possible. This boat is used maybe 10 times a summer, mostly to ski and kneeboard behind.What would you guys do if you were in my shoes? I may have access to a 351 for $300.00 and that is much cheaper than the $1400.00 rebuilt marine engine.Thanks,Mike

  2. #2
    Chief Petty Officer
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    Default Re: Replacement OMC 5.8 351W

    The cam is much different than a truck or van engine.Then there is more to it.Shop around for a marine engine,you will come out in the long run.How are the heads?Why not go with a short block? Cost around $500.

  3. #3
    Admiral tommays's Avatar
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    Default Re: Replacement OMC 5.8 351W

    we used jasper not the cheepest but they stand behind there work http://www.jasperengines.com/ tommays
    If a dirty bottom slows you down what do think it does to your BOAT

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  4. #4
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    Default Re: Replacement OMC 5.8 351W

    Thanks for the replies.The heads are perfect. I had them checked before, just have to fix one of the threads where the intake mounts because the bolt broke off inside, but nothing major. I had them planed and preasure tested. Valves look good.Could I use the same cam that came in the original engine? I know I can use the same heads. I thought for some reason that once the cam was taken out, you have to be careful not to use it again because of the chance of it getting out of round if you lay it down. Is that an old wives tale? I have kept it in a box and it is still in good condition, not dropped it or anything.What parts can I use again if I go with the short block? What exactly comes in the short block?Thanks again.Mike

  5. #5
    Petty Officer 1st Class olbuddyjack's Avatar
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    Default Re: Replacement OMC 5.8 351W

    I thought for some reason that once the cam was taken out, you have to be careful not to use it again because of the chance of it getting out of round if you lay it down.
    Never heard that one before. Heck, new ones come in a box laying down.I've reused cams before, just make sure you use the same lifter on the lobe it came from.A short block is your lower recipricating assembly, crank, pistons, rods(rodbolts )timing chain and cam. No heads, manifolds, oil pan and such.All you old stuff should bolt right on.

  6. #6
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    Default Re: Replacement OMC 5.8 351W

    olbuddyjack,It was new to me also, but it is what I heard at one time or another so I figured I would ask. Can I use new lifters with the old cam? I will probably replace the pushrods also. tommays,I looked at Jasper Engines and they want $2,200.00 for a reman. That is kinda high. I understand why though, it is a completely rebuilt engine. Just a lot more than I want to spend right now. prockvoan,Where can I look for a marine short block for $500? All the prices I have seen are around $1,400.00.As far as the block goes, does it have to be marine or could I use a standard block with my marine heads and cam?Also, what about the marine crank? Is that different from a standard crank?Mike

  7. #7
    Petty Officer 1st Class olbuddyjack's Avatar
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    Default Re: Replacement OMC 5.8 351W

    There may be some controversy on this one but I would use new lifters on the old cam. Some say that since the lifters and lobes wear in together that replacing one without the other will cause premature wear. I havent seen it myself.Marine engines are basicaly truck/industrial engines with brass core hole plugs and other marine specific parts. A car block will work but may not hold up as well.Do a search on member name "boomyall". He has been working on one of these motors(actually two)for a while and is quite knowlegable on them.I'm supprised he hasn't look in yet, must be fishin'

  8. #8
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    Default Re: Replacement OMC 5.8 351W

    I searched for that name and it says there is no name of 'boomyall' on this board?Mike

  9. #9
    Commander Lou C's Avatar
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    Default Re: Replacement OMC 5.8 351W

    boomyal
    1988 Four Winns 200 Horizon
    4.3 OMC Cobra

    98 Jeep Grand Cherokee 4.0 Selectrac
    07 Jeep Grand Cherokee Limited 5.7 Quadradrive II

  10. #10
    Petty Officer 1st Class olbuddyjack's Avatar
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    Default Re: Replacement OMC 5.8 351W

    Oh crap, Im sorry, I misspelled it. Its "boomyal".One L. Sorry bout dat.

  11. #11

    Default Re: Replacement OMC 5.8 351W

    I have the same problem I got 13hours out of a rebuilt a connecting rod went through the oil pan , I now have another 351 but I am not sure on what kind of camshaft to purchase to convert so it will hold up in my boat.. any Ideas would be great
    thank you
    Louie

  12. #12
    Commander zbnutcase's Avatar
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    Default Re: Replacement OMC 5.8 351W

    Quote Originally Posted by ecom2b View Post
    I have the same problem I got 13hours out of a rebuilt a connecting rod went through the oil pan , I now have another 351 but I am not sure on what kind of camshaft to purchase to convert so it will hold up in my boat.. any Ideas would be great
    thank you
    Louie
    Start your own thread please instead of replying to a 5 yr old post.
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