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Pulled my Mercruiser 7.4L out of the boat today

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  • Pulled my Mercruiser 7.4L out of the boat today

    I pulled my 20 year old Mercruiser 7.4L (454) out of the boat today. It is in need of a top-end rebuild (valves and head gasket), so I thought it would be easier all-round if I pulled the engine.

    Here is a photo of the engine safely on the ground ready for tear-down. I did a leak test to see where the problems were prior to pulling the heads. Cylinders 1,2,8 are OK . . . 3,4,7 are leaking via the intake valve . . . 5,6 are leaking via the exhaust valve.



    I still need to remove the exhaust manifolds prior to pulling the heads off. Lots of rust on the exhaust bolts, I will need to drill the heads off a few of them.
    Best regards,
    Formula 330 Sun Sport
    Twin Mercruiser 7.4 LX MPI (0F802036, 0F802039), Bravo 3's (0F806198, 0F806199)
    1969 Mercury 7.5 HP Outboard (26346XX)
    My F-330 Web Site: http://home.comcast.net/~tpenfield/F...30SS/Home.html
    My F-242 Web Site: http://home.comcast.net/~tpenfield/W...Boat_Page.html
    Member of the Month - February 2013
    http://www.iboats.com/blog/tpenfield...-of-the-month/


  • #2
    Re: Pulled my Mercruiser 7.4L out of the boat today

    Been there, done that! It's much easier than leaving it in the boat.
    Do you have a question?

    Comment



    • #3
      Re: Pulled my Mercruiser 7.4L out of the boat today

      Originally posted by tpenfield View Post
      I pulled my 20 year old Mercruiser 7.4L (454) out of the boat today. It is in need of a top-end rebuild (valves and head gasket), so I thought it would be easier all-round if I pulled the engine.

      Here is a photo of the engine safely on the ground ready for tear-down. I did a leak test to see where the problems were prior to pulling the heads. Cylinders 1,2,8 are OK . . . 3,4,7 are leaking via the intake valve . . . 5,6 are leaking via the exhaust valve.



      I still need to remove the exhaust manifolds prior to pulling the heads off. Lots of rust on the exhaust bolts, I will need to drill the heads off a few of them.
      Being a 20 year old engine, since you have her out and re-doing the heads, would it not be adventageous to do the rings, timing chain / gears and lower end also? In the years I have been rebuilding engines ((probably over a hundred (engines, not years) by now)), I have found that older engines tend to need rings shortly after doing the heads. I summize this is due to engine "aging gracefully" as a unit tend to age "less gracefully" after the compression is bumped up by the new valves and head gasket start stressing the capability of the 20 year old rings to accomidate the higher compression.

      Getting the motor out and heads off for rebuilding is alot of work and would be a shame if it all had to happen again in the near future if a bearing started making noise or the motor started burning oil / losing compression if the rings gave out under the new stress of having 100% compression.

      Just my opinion, I would do a whole re-build. You may discover it even needed new pistons due to an out of spec bore. The minus of this, it can be a little pricey. The plus, you have a brand spanking new engine in the process, built the way YOU want it.

      My wife is dreading the day I need to do something major on my 20 year old 454, knowing it will not the same engine when it goes back in. ( Dare I say a few upgrades to make it a little bigger, alot stronger and a tad more powerful). The perfect winter project..................
      '92 Chaparral 2550 SX Sport
      454 BBC Mercruiser Bravo 1
      Tow with '04 F150 Larriat SuperCab 4x4 5.4 Triton
      US Coast Guard Aux.

      Comment



      • #4
        Re: Pulled my Mercruiser 7.4L out of the boat today

        Yes, I am considering a complete re-build, but I'm concerned about it becoming too big of a project (labor and $$$).

        Once I get the heads off, then that will be the deciding factor. The engine has 540 hours on it, so it is kind of on the edge.

        If I were to do rings, then it would make sense to do the camshaft and crankshaft bearings. At that point, it would be worth buying a re-build 'kit'. The thing I worry about is getting an inferior kit that has sub-standard parts.

        Anyone have advice on the better brand/source of rebuild kits for a 454 ???
        Best regards,
        Formula 330 Sun Sport
        Twin Mercruiser 7.4 LX MPI (0F802036, 0F802039), Bravo 3's (0F806198, 0F806199)
        1969 Mercury 7.5 HP Outboard (26346XX)
        My F-330 Web Site: http://home.comcast.net/~tpenfield/F...30SS/Home.html
        My F-242 Web Site: http://home.comcast.net/~tpenfield/W...Boat_Page.html
        Member of the Month - February 2013
        http://www.iboats.com/blog/tpenfield...-of-the-month/

        Comment



        • #5
          Re: Pulled my Mercruiser 7.4L out of the boat today

          First thing you should do is pull the heads so you can inspect cylinder wear.

          Then find an excellent auto machine shop to work with. They can do the head work and advise you on rebuilding the rest of the engine. A good quality machine shop will also be familiar with marine engines.

          Last time I was rebuilding an inboard/outboard motor, the pistons, connecting rods and bearings were Ford parts--and I didn't have to buy the ridiculously expensive Mercruiser parts. Most internal engine parts are available outside the engine manufacturer.

          You'll want to make sure the lower end of the motor is 100% before you waste time and money reassembling and reinstalling this engine. 570 hours is comparable to 30,000 highway miles on a car, so the low end may still be perfectly good. If so, you could always just change rings and go about your day. It comes down to how well maintained your engine has been, and how hard it's been run over the years. That's where quality advice comes in.

          Comment



          • #6
            Re: Pulled my Mercruiser 7.4L out of the boat today

            If it has good ring tension, cylinder walls look ok(no large ridge), bearings look good, I would not be scared to re- run the short block. I would put on a new timing chain. Of course that doesnít mean you canít change the cam and lifters also

            Comment



            • #7
              Re: Pulled my Mercruiser 7.4L out of the boat today

              Once I get the heads off, then that will be the deciding factor. The engine has 540 hours on it, so it is kind of on the edge.
              Ayuh,... On the Edge,..??

              'ell, unless abused, it's barely broken in....

              2,000/ 3,000hrs is on the edge...
              Any Grease is Better,..... Than No Grease at All.......

              Comment



              • #8
                Re: Pulled my Mercruiser 7.4L out of the boat today

                A few different ideas so far, which I like. I'm thinking that if I plan on replacing the rings, I can get a good look at the crankshaft and piston bearings to see if there is any adverse wear.
                Best regards,
                Formula 330 Sun Sport
                Twin Mercruiser 7.4 LX MPI (0F802036, 0F802039), Bravo 3's (0F806198, 0F806199)
                1969 Mercury 7.5 HP Outboard (26346XX)
                My F-330 Web Site: http://home.comcast.net/~tpenfield/F...30SS/Home.html
                My F-242 Web Site: http://home.comcast.net/~tpenfield/W...Boat_Page.html
                Member of the Month - February 2013
                http://www.iboats.com/blog/tpenfield...-of-the-month/

                Comment



                • #9
                  Re: Pulled my Mercruiser 7.4L out of the boat today

                  Iíd start with the center main cap and then the thrust main, from there a couple rod caps. This all can be done without too much taking apart. If you donít have much experience with this, the caps and bearings MUST go back from where the were taken and use of proper torque specs is imperative. You can post pics of the bearings if needed. (Sorry if you knew all this)
                  Like Bond-o said, if it was well maintained... oil changed, not overheated, it should be just getting broken in well as far as the rings go.

                  You did mention valves in your o/p, any piston to valve contact, ie bent valves? Was blown head gasket do to overheating?

                  Comment



                  • #10
                    Re: Pulled my Mercruiser 7.4L out of the boat today

                    Originally posted by joewithaboat View Post
                    Iíd start with the center main cap and then the thrust main, from there a couple rod caps. This all can be done without too much taking apart. If you donít have much experience with this, the caps and bearings MUST go back from where the were taken and use of proper torque specs is imperative. You can post pics of the bearings if needed. (Sorry if you knew all this)
                    Like Bond-o said, if it was well maintained... oil changed, not overheated, it should be just getting broken in well as far as the rings go.

                    You did mention valves in your o/p, any piston to valve contact, ie bent valves? Was blown head gasket do to overheating?
                    The engine started to run hot - 180 instead of the normal 155 - I did all the cooling system diagnosis to no avail. If I ran at lower RPM (under 2K), it was fine, at cruising speeds it ran up to 180 and stayed. Idle back down, temp came back down.

                    This problem came on suddenly. Sooo, I finally did a leak test and got lots of leak on the middle cylinders (3,4,5,6). It appeared that I was getting air up the carb and up the exhaust manifold. I confirmed yesterday that I am getting intake valve leak on 3 cylinders and exhaust valve leak on 2 cylinders. The remaining 3 cylinders are 'OK'. I never was able to confirm the head gasket being blown, so that will have to wait for the the tear-down

                    The engine has been well cared for (by me) I got the boat with 305 hours and have put on another 235 hours over 7 years.. Rarely do I run it over 3800 RPM, Change the oil every 50 hours or seasonally, no abuse or things like that. So, I am expecting the bottom end to be in good shape.
                    Best regards,
                    Formula 330 Sun Sport
                    Twin Mercruiser 7.4 LX MPI (0F802036, 0F802039), Bravo 3's (0F806198, 0F806199)
                    1969 Mercury 7.5 HP Outboard (26346XX)
                    My F-330 Web Site: http://home.comcast.net/~tpenfield/F...30SS/Home.html
                    My F-242 Web Site: http://home.comcast.net/~tpenfield/W...Boat_Page.html
                    Member of the Month - February 2013
                    http://www.iboats.com/blog/tpenfield...-of-the-month/

                    Comment



                    • #11
                      Re: Pulled my Mercruiser 7.4L out of the boat today

                      Originally posted by tpenfield View Post
                      Yes, I am considering a complete re-build, but I'm concerned about it becoming too big of a project (labor and $$$).

                      Once I get the heads off, then that will be the deciding factor. The engine has 540 hours on it, so it is kind of on the edge.

                      If I were to do rings, then it would make sense to do the camshaft and crankshaft bearings. At that point, it would be worth buying a re-build 'kit'. The thing I worry about is getting an inferior kit that has sub-standard parts.

                      Anyone have advice on the better brand/source of rebuild kits for a 454 ???
                      All the "GOOD STUFF" for BBC's. Even marine rated parts.

                      http://www.jegs.com/

                      http://www.summitracing.com/
                      '92 Chaparral 2550 SX Sport
                      454 BBC Mercruiser Bravo 1
                      Tow with '04 F150 Larriat SuperCab 4x4 5.4 Triton
                      US Coast Guard Aux.

                      Comment



                      • #12
                        Re: Pulled my Mercruiser 7.4L out of the boat today

                        Ted
                        Good job on being aware of your gauges. Was the motor otherwise running well, except the temp? What method did you use for the leakdown test? 180deg is not hot enough to hurt anything so i bet if it was running well otherwise your short block might check out fine.

                        p.s. I have always liked those Formula hulls they handle H/P upgades well i bet, sure would be tempting.
                        Last edited by joewithaboat; October 3rd, 2011, 10:08 AM. Reason: missed a word

                        Comment


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