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Oil pump in a Mercruiser 3.0.

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    Oil pump in a Mercruiser 3.0.

    I am assembling my 1st boat motor. I am ready to install the oil pump, I have 3 used pumps to choose from. Is there a gasket at the mounting surface? And Is there a way to bench test ?

    #2
    No and no!
    Rick E. (aka RicardoMarine) Gresham, Oregon
    2850 Bounty Sedan Flybridge model
    Twin 280 HP 5.7's w/ Closed Cooling
    Volvo Penta DuoProp Drives
    Kohler 4 CZ Gen Set

    Please, no PMs. Ask your questions on forum.

    Comment


      #3
      Why would a person use an old oil pump ?
      Asking for a friend.
      " WET EVER "
      1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
      mmsi 338108404
      mmsi 338124956
      "I started with nothing and still have most of it left"

      Comment


        #4
        Originally posted by dktool View Post
        Why would a person use an old oil pump ?
        Asking for a friend.
        The General Motors twin gear, semi-positive displacement oil pump is bulletproof.
        Rick E. (aka RicardoMarine) Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Please, no PMs. Ask your questions on forum.

        Comment


          #5
          Originally posted by 2850Bounty View Post

          The General Motors twin gear, semi-positive displacement oil pump is bulletproof.
          From that I'll conclude you don't put a new pump in your engine builds.
          " WET EVER "
          1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
          mmsi 338108404
          mmsi 338124956
          "I started with nothing and still have most of it left"

          Comment


            #6
            Originally posted by dktool View Post
            From that I'll conclude you don't put a new pump in your engine builds.
            That would be incorrect!

            Boat boy is assembling an engine.
            He has three used oil pumps to choose from.
            While I would not install a used pump, if he removes the cover plate and examines the gears and drive shaft of each one, he could certainly use the best of the three.


            Rick E. (aka RicardoMarine) Gresham, Oregon
            2850 Bounty Sedan Flybridge model
            Twin 280 HP 5.7's w/ Closed Cooling
            Volvo Penta DuoProp Drives
            Kohler 4 CZ Gen Set

            Please, no PMs. Ask your questions on forum.

            Comment


              #7
              Ok.... I did not mean to cause a fuss. However I did take the following; No I do not need a gasket which I guess means a metal to metal seal or not to seal or maybe it's not supposed to seal? And. There is no way to bench test the pump so without bench testing I have no idea if it works or not. And from that maybe I should purchase a new one ?? Or take the used one apart and check the gears?

              Comment


                #8
                After a quick search of the world wide web. I found this pump listed as cheap as $28 for a used one. And as high as $300 for what I guess is a new one (the add didn't say). So the $300 option is out. Not happening. Being that there were several options for used oil pumps.... May I ask if a rebuild is possible?

                Comment


                  #9
                  Originally posted by Boat boy View Post
                  Ok.... I did not mean to cause a fuss. However I did take the following; No I do not need a gasket which I guess means a metal to metal seal or not to seal or maybe it's not supposed to seal? And. There is no way to bench test the pump so without bench testing I have no idea if it works or not. And from that maybe I should purchase a new one ?? Or take the used one apart and check the gears?
                  Are you in the US where parts are plentiful, or are you somewhere that has poor parts access or prices are ridiculous to get delivered to you?

                  Edit a few minutes later- Oh, you're the guy that goes to Lanier...Sorry, I was skimming the post and was a bit confused.

                  I would encourage you to get a new oil pump rather than a used one. The thing is the "heart" of the engine and boats have a hard life compared to a car engine.

                  The other guys can help you with reliable and affordable sources.

                  I have no direct experience building a Mercruiser.
                  Present Boat- 2018 VR5 4.5/200hp Mercruiser
                  Last Boat- 1998 Capri 1950CL 3.0 Mercruiser

                  Comment


                    #10
                    $40.00 plus tax for a new Melling pump....with gasket.

                    https://www.amazon.com/Melling-M62-P.../dp/B001P2DC52
                    " WET EVER "
                    1989 2459 TROPHY OFFSHORE 5.8L COBRA / SX
                    mmsi 338108404
                    mmsi 338124956
                    "I started with nothing and still have most of it left"

                    Comment


                      #11


                      Originally posted by Boat boy View Post
                      Ok.... I did not mean to cause a fuss.
                      You did not.
                      Every once in a while, we like to get our panties in a wad with each other.
                      All is good!
                      😉


                      However I did take the following; No I do not need a gasket which I guess means a metal to metal seal or not to seal or maybe it's not supposed to seal?
                      The two machined surfaces make an adequate seal.
                      A 40/50psi leak here would be a very small leak, and it would be within the oil pan area.


                      And. There is no way to bench test the pump so without bench testing I have no idea if it works or not. And from that maybe I should purchase a new one ??
                      Or take the used one apart and check the gears?
                      That is certainly easy enough to do.
                      I believe that your pump's bottom plate is secured with 4 small bolts.
                      Remove the bolts, and the gears will be exposed.
                      Pull the gears and examine them and the shafts.

                      There are no shims to be concerned with.

                      I would leave the relief valve alone.



                      May I ask if a rebuild is possible?
                      I wouldn't call it a "rebuild", it would be more of an inspection and re-assembly....... but yes, parts are available.

                      The GM twin gear style engine oil pump can go for up to 200K + miles in a car engine.
                      The pump does not know nor care if it is in a Car engine or a Marine engine.
                      The work load is no greater in a Marine engine than it is in a Car engine.
                      The gears are not undergoing a heavy load mechanical function...... they are displacing engine oil ONLY.
                      The gears and shafts are subject to complete lubrication during engine operation.
                      The gear teeth are straight cut ...... which means no up/down side load thrust


                      These pumps are capable of producing 200+ psi. The relief valve maintains correct engine oil pressure.


                      Click image for larger version  Name:	GM 3.0 L oil pump system 2 .jpg Views:	0 Size:	224.1 KB ID:	651653

                      Click image for larger version  Name:	GM 3.0 L oil pump system.jpg Views:	0 Size:	149.6 KB ID:	651652
                      Rick E. (aka RicardoMarine) Gresham, Oregon
                      2850 Bounty Sedan Flybridge model
                      Twin 280 HP 5.7's w/ Closed Cooling
                      Volvo Penta DuoProp Drives
                      Kohler 4 CZ Gen Set

                      Please, no PMs. Ask your questions on forum.

                      Comment


                        #12
                        2850Bounty

                        I might not have gone as deeply as I should have in my earlier post.

                        Marine vs Automotive

                        Marine engines operate at higher RPMs with higher loads almost every minute they are operated (except while trolling) compared to a car engine which has transmission gears and only needs a small amount of horsepower at cruising speed.

                        I agree that the boat's actual oil pump does not work any harder than a car's.

                        I just wanted his "heart" to be as fresh and as strong as possible with the smallest chance of any wear causing decreased performance as time marches on.

                        I want all his bearings to last a very long time!

                        Great pics, by the way!
                        Present Boat- 2018 VR5 4.5/200hp Mercruiser
                        Last Boat- 1998 Capri 1950CL 3.0 Mercruiser

                        Comment


                          #13
                          When I rebuilt, some engine manuals provide gear clearance dimensions you can measure to determine gear, housing or end plate wear.

                          A quick interweb search will provide numerous links. Here is an example: Click image for larger version

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                            #14
                            I thank you gentleman. I ended up choosing 2 out of the 3 looked to be in better shape on the outside. Took both apart and it was very clear which one appeared to be in much better shape. The shaft on one had plenty of wear along with some strange black paste. The one I used had practically none and was very clean inside.i could spin it with my fingers it was nice and smooth. I don't have anything to measure side movement but I sure couldn't feel any. Inside the plate I could see a faint whispy ware mark but couldn't feel it with my finger. I lapped.it a little cleaned it all and bolted it on. Now I have bought 2 one piece oil. Pan gaskets and both were wrong. Dose anyone make a one piece after market oil pan gasket?
                            I thank you in advance for any advice or knowledge

                            Comment


                              #15
                              I have another question I have a cheap somewhat vague manual that says not to use any permatex with the head gasket . I read on the World wide web and some say yes do use it. Well which is it??
                              Again I thank you all for your input.

                              Wow... It's 11:00 pm again !!

                              Comment

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