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  1. #1
    Petty Officer 2nd Class
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    Default What Oil Weight should I use ???????

    I have a 1990 Regal 233 XL Ambassador (Cabin Cruiser Type) - carburated Mercruiser 5.7 (350 ci). I live near the border of Missouri & Arkansas, all lake water use. I would like to know what weight and brand of oil to use. I've had a number of people tell me straight 40 or 30, 10-40 or 10-30 and use mobile1. Mostly I heard straight 30 for Northern boats and straight 40 for Southern. Thanks to all that reply!

  2. #2
    Chief Petty Officer
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    Default Re: What Oil Weight should I use ???????

    10w-30 is the most commonly used for any small block

  3. #3
    Fleet Admiral HT32BSX115's Avatar
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    Default Re: What Oil Weight should I use ???????

    Hmm,


    You missed yesterdays oil thread! Your's can be today's Seems like this question is asked about every day or so.....


    If you do not want to use the oil that Mercury recommends,

    You can use what ever you want. Marine engines don't fail due to brand or type of oil. Everything has been tried successfully.


    Cheers,


    Rick
    73 de Rick
    ----------------------------------------------------------------------------------
    I use xxx oil and have never had a problem........
    1987 FourWinns 211 Liberator, 7.4L- Bravo III installed by ME,
    Formerly OMG 460 King Kobra powered
    1947 Stinson 108-2 Station Wagon
    , Franklin 6A-335B. Hartzell CS 2-blade prop
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    All PM's cheerfully answered! Please ask tech questions in the appropriate forum so everyone's included

  4. #4
    Commander Lou C's Avatar
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    Default Re: What Oil Weight should I use ???????

    Merc says their 25/40 or straight 40...
    I would not use a 10w-30 in a marine inboard...more likely to break down...as long as your boating temps are moderate the straight 40 will be fine...
    OMC and Volvo recommended straight 30....Merc straight 40 for the same base engines...go figure...
    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

  5. #5
    Rear Admiral Fishermark's Avatar
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    Default Re: What Oil Weight should I use ???????

    Quote Originally Posted by Lou C View Post
    Merc says their 25/40 or straight 40...
    Well, Mercruiser has a few more choices than that. And the straight 40 or straight 30 depend upon the temp....



  6. #6
    Petty Officer 2nd Class
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    Default Re: What Oil Weight should I use ???????

    Now I'm confused????????
    Weather temps would be around 70-99 degress.
    I'd be running 15-20 minutes at a time.
    I'm thinking straight 40.
    Any other opinions, please advise!
    Thank you

  7. #7
    Rear Admiral Fishermark's Avatar
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    Default Re: What Oil Weight should I use ???????

    Quote Originally Posted by Johnny Be Cool View Post
    I'm thinking straight 40.
    That'll work just fine.

  8. #8
    Cadet iconracing's Avatar
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    Default Re: What Oil Weight should I use ???????

    just use straight 40

  9. #9
    Captain Philster's Avatar
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    Default Re: What Oil Weight should I use ???????

    Anything from straight 40 on up the chart to other options listed. Straight 40, according to Merc, is the 4th best option.
    Checkmate 2400BRX/Optimax 300xs
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    Alumacraft 17 w/ Merc 40 4S

    Date an I/O, but marry an outboard!


  10. #10
    Senior Chief Petty Officer
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    Default Re: What Oil Weight should I use ???????

    Quote Originally Posted by Johnny Be Cool View Post
    I have a 1990 Regal 233 XL Ambassador (Cabin Cruiser Type) - carburated Mercruiser 5.7 (350 ci). I live near the border of Missouri & Arkansas, all lake water use. I would like to know what weight and brand of oil to use. I've had a number of people tell me straight 40 or 30, 10-40 or 10-30 and use mobile1. Mostly I heard straight 30 for Northern boats and straight 40 for Southern. Thanks to all that reply!
    I use 10-40 on all motors and never had a problem. Great in all kinds of weather. Use a top notch brand.

  11. #11
    Petty Officer 1st Class IES99's Avatar
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    Default Re: What Oil Weight should I use ???????

    Tomorrow it is my turn to ask this question.

    It isn't easy being GREEN

  12. #12
    Petty Officer 3rd Class carolynrose's Avatar
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    Default Re: What Oil Weight should I use ???????

    Just my 2 cents. In my 30+years as a GM master tech, all the classes I've been to, GM was very insistant not to use 10w40 in any of their engines. There a ton of 350 GM engines out there in boats. Unlike a car engine, boat engines run at a continuosly higher rpm. I would recommend the 30 or 40 weight oil that the service manual says. It is very unlikely that you operate your boat engine in below freezing temps, so the need for the 10w oil in multi viscosity oils isn't needed. Remember 10w30, the w stands for winter

  13. #13
    Petty Officer 2nd Class
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    Default Re: What Oil Weight should I use ???????

    Thanks to all for giving your opinions.
    I'm thinking of staying with a straight 30 or 40, therefore what is the difference between the two and their applications.
    Under what circumstance should I run 40 or 30 weight.
    Thank you!!!!

  14. #14
    Senior Chief Petty Officer elkhunter338's Avatar
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    Default Re: What Oil Weight should I use ???????

    30 is going to be less thick when cold. if you are always boating with temps well above freezing go with either 30 or 40.
    I would stick with a diesel grade oil, in a 30 or 40 weight. you will not have any trouble.

  15. #15
    Petty Officer 2nd Class
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    Default Re: What Oil Weight should I use ???????

    Go Figuire???????????
    Mercruiser suggested Quick Silver 25w-40 or straight 30
    I appreciate everyone's opinion. Thank You and Happy boating!!!!!!!!!

  16. #16
    Senior Chief Petty Officer
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    Default Re: What Oil Weight should I use ???????

    I use 10/40 and never had a problem but straight 40 is fine.

  17. #17
    Rear Admiral Howard Sterndrive's Avatar
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    Default Re: What Oil Weight should I use ???????

    nothing that starts with a 10 or a 5 unless boat has an engine oil cooler (i.e. some Volvo Penta)
    i.e. I agree with Mercruiser
    Baba-buoy.

  18. #18
    Senior Chief Petty Officer
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    Default Re: What Oil Weight should I use ???????

    Thats true so its really just for starting. Sometimes I think the engineers put out those specs because they don't do enough research.

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