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    Replacing Engines on 96 avanti 3258

    Last February my wife and I purchased a 96 Bayliner 3258. I got a great deal on it Knowing that it was not in the best mechanical shape and had been sitting for a long time. I got the engines going and was able to make the 300 mile journey home, as well as enjoy 100+ hours of cruising in the Lower Chesapeake bay area this past summer, Towards the end of the season i starting have multiple issues with both engines, oil leaks, blow by [ oil coming out of the exhaust ] hard starts, overheating ect. you name it. but i was able to diagnosis, fix what i could as we went, and still able to enjoy an extended season, going up until Christmas. I had the boat hauled out, and as i expected the engines are pretty much toast and now is the time to replace them. Current engines are 95 non vortec Mercruiser 5.7l 260 hp, both are standard rotation with bravo 2 outdrives. I have my mind up to 2 different replacement options, and would love you to get ya'lls feed back and any information you have. Please keep in mind that i am Making the dicision to hire a mechanic to do the work instead of myself beacuse #1 i have many other projects planned for the boat that i will be doing myself while the engines are replaced. And this is a busy time of year at work for me 60+ hours per week. Also i do have a budget going into this, if money was no object i would go a different route

    option # 1

    Buy 2 non vortech Reman longblocks from Jegs, replace the manifolds and risers [ extremely bad need to be replaced] and re use current intake manifold carbs, and all other engine components. with labor, parts, shipping ect, I calculate this option to cost $ 7,400 total hp 520

    option # 2

    Buy partial Vortech assy from Center state marine, these are reman Vortech longblocks, with new intake manifold, new edelbrock carbs, delco ingition, and new circulating water pump. and new electric fuel pumps, than i will also be buying new manifolds and risers, and reusing other assy components from old engines. with the labor, parts, shipping and taxes I calculate this option the cost $ 10,680 total hp 660


    Would love to hear what option you guys think i should go with ? if you think the vortec and extra hp is worth it ?and if you have any other ideas ? or any experience with this process or with these vendors ? PLEASE keep in mind and respect the fact that i can NOT afford anything more expensive then option number 2
    1998 bayliner 2355
    mercruiser 5.7
    alpha one

    #2
    Rather than looking at just horsepower, look at the torque curve in relation to your known cruising rpm range. I’m assuming you have the mechanic hours in there, but what is your basis of that estimate? That’s one of many places that can get away from you. What about peripherals? All new hoses, steam cleaning the engine bay, sundry parts like the coupler bearing, possibility new propellers. How much did you include for unknown unknowns? You may have a factor in there for known unknowns, but the unk-unks are sneaky.
    When I repowered my previous boat in 2001 I bought new power and drive packages. The transom reinforcement had to be replaced, new gauges, control cables, battery cables and wire harness were all installed. I did the work myself with help from my sons. The power packages cost around 16K and I spent another 4K on everything else. It took me nine weeks and the yard I was in was $200/mo.

    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    MMSI 367770440

    Comment


      #3
      Originally posted by Pcpete View Post
      Rather than looking at just horsepower, look at the torque curve in relation to your known cruising rpm range.
      Pete is right on!


      Also, be aware of the horse power number games that are played.
      Look closely at the RPM at which the HP and Torque ratings were taken.

      When the first SBC 5.7L Vortec made it's way into the Marine world, we would see advertised hp ratings of 315 and 320.
      When you looked at the specs, you would see that these ratings were taken at/near 5,300/5,400 RPM.
      I don't know anyone who cruises at, or even near, 5,300 RPM!


      But back to torque.

      All GM produced SBC 5.7L marine engines are going to be fitted with the GM Full Dished pistons.
      Most all re-builders also use this piston!

      They use this piston because;
      ..... one piston p/n fits all 8 bores.
      ..... they are inexpensive.
      ..... the guy installing the pistons onto the connecting rods can be smoking pot.


      This style piston is prone to causing Marine Load Detonation because the dished area gives a portion of the flame front a place to hide!
      We do not want the flame front to hide!

      The cure is to hold back on ignition TA, of which makes for less torque.

      If up for the task, have a pair of these custom built using a much better Q/E piston profile..... especially if you are considering going with the Vortec cylinder heads.

      Then there is also the option of going with a pair of 6.2L (377 cu in) or 6.3L (383 cu in) SBCs, commonly known as the "stroker" engine.

      But again, have these custom built using a Q/E style piston..... especially if you go with the Vortec heads!
      No other major changes need to be made in the build.

      The Q/E (quench effect) is not necessarily a hot rod or high performance thing, nor is it a "break the bank" thing.
      A good set of Q/E pistons will cost you approx $250 more than the silly, no good, poor choice, GM Full Dished pistons will.
      Shop labor should be very close to the same.

      Going this route gives us a proper combustion chamber design that is far less prone to Marine Load Detonation.
      With this design, now ignition TA (total advance) can be where it should be in order to produce more engine torque!

      Fuel economy is also improved along with better performance.




      One last thing.
      If you do decide to have a pair custom built with the Q/E style pistons, and if the shop person was to give you that "Deer in the Headlights" look, find another shop!
      Most any good machine shop will be capable of doing this build for you.


      .
      Rick E. 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

      Comment


        #4
        I know I’m spending your money but if you are boating in brackish or salty water and installing reman or new engines I would for sure install closed cooling. This more than nearly anything else you can do will greatly extend the life span of the engines; make it easier to winterize and add resale value for a knowledgeable buyer.

        Closed cooling + remote mount oil filters a must esp with twin engines!
        88 Four Winns 200 Horizon 4.3 OMC
        98 Jeep Grand Cherokee 4.0/Selectrac
        07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

        Long Island Sound Region

        Comment


        • builderdude
          builderdude commented
          Editing a comment
          Agree👍🏼

        #5
        When I had to repower in 2016 I bought a brand new Vortec (full dished piston) to replace the 97' 5.7 260 HP and have never regretted the extra HP and power range over the old engine.. This cost about the same price as a reman 5.7 260 HP and had the boat running in one week. I bought a new carb intake for it and rebuilt my old carb, also added partial closed cooling.
        1997 Maxum 2400 SCR 5.7LX Bravo II

        Mike

        Comment


          #6
          Originally posted by 88fourwinns View Post
          I know I’m spending your money but .........

          Closed cooling + remote mount oil filters a must esp with twin engines!
          In my opinion, those two items, along with remote oil drain systems, are very important items.
          Even if NOT in salt or brackish water, a Closed Cooling System will extend the life of your engines, and it will make engine winterizing pretty much goof proof.


          If budget will not allow, we will start a "go fund me" for you!

          I'll donate the first $10.


          .


          Rick E. 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

          Comment


            #7
            Thanks for the info, I probably need to do some more research on the cost of adding closed cooling, the boat mainly does run in salt water, I do flush the engines with salt away after every weekend, I know that doesn't do to much, and i would love to not have to spend 20 mins every sunday doing that. i do already have remote oil filter, and electric transfer pump for easy oil changes
            1998 bayliner 2355
            mercruiser 5.7
            alpha one

            Comment


              #8
              Forgot to mention that if you go with the Vortec you will need to convert to an electric fuel pump and add an oil pressure switch to power it. Easy enough to do.
              1997 Maxum 2400 SCR 5.7LX Bravo II

              Mike

              Comment


              • builderdude
                builderdude commented
                Editing a comment
                vortec style heads and pistons can be bolted up to the earlier style block too😁

              #9

              Originally posted by bprinty View Post
              Thanks for the info, I probably need to do some more research on the cost of adding closed cooling, the boat mainly does run in salt water, I do flush the engines with salt away after every weekend, I know that doesn't do to much, and i would love to not have to spend 20 mins every sunday doing that.
              Salt water corrosion and salt crystalization never sleep.
              We can perhaps slow it down some, but once is begins, there is no stopping it.


              i do already have remote oil filter, and electric transfer pump for easy oil changes
              If you have bungs TIG welded to the bottom areas of your new oil pans, and use 1/2" ID oil resistant hoses, oil changes will be even easier and faster!


              Originally posted by Nauti_Mike View Post
              Forgot to mention that if you go with the Vortec you will need to convert to an electric fuel pump and add an oil pressure switch to power it. Easy enough to do.
              That's right.
              There is no longer a push rod port nor a usable mounting location for the mechanical fuel pump.
              Very easy to add!



              Originally posted by Dave
              Vortec style heads and pistons can be bolted up to the earlier style block too😁
              Correct!
              The only things gained by the Vortec cylinder heads are the swirl points (at the quench surfaces), and the larger intake runners.
              The swirl points do ZERO when used with the GM Full Dished pistons.





              Click image for larger version  Name:	Quench and Squish area  for Vortec SBC .jpg Views:	0 Size:	352.9 KB ID:	556893
              This image may better explain the the Quench Effect area.

              Note the black dotted lines indicating the piston's dished area.
              The dished area on the left side comes up underneath the cylinder head's quench surface.
              The dished area on the right side is underneath the combustion chamber area ONLY!



              Click image for larger version  Name:	Quench and Squish area explained 4.jpg Views:	0 Size:	121.2 KB ID:	556894
              Rick E. 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

              Comment


                #10
                Bprinty, have you thought about your future boating needs at all? Is this your end all boat or do you think you might want to step up to a bigger boat in a year or two? If I was thinking about moving to a larger vessel or a different style sometime in the next few years I’d be very careful about how much I’d want to dump into this boat. Reliability and cost would drive my decision vs horsepower and closed cooling unless I planned to keep this boat for several years. Pete’s very correct when he opines that engine projects costs can easily go over budget, way over budget! YMMV
                Jim Gandee
                1989 3888
                Hino 175's
                Fire Escape
                [email protected]
                Alamitos Bay, SoCal

                Comment


                  #11
                  Originally posted by Jim_Gandee View Post
                  Bprinty, have you thought about your future boating needs at all? Is this your end all boat or do you think you might want to step up to a bigger boat in a year or two? If I was thinking about moving to a larger vessel or a different style sometime in the next few years I’d be very careful about how much I’d want to dump into this boat. Reliability and cost would drive my decision vs horsepower and closed cooling unless I planned to keep this boat for several years. Pete’s very correct when he opines that engine projects costs can easily go over budget, way over budget! YMMV
                  Good point, after I do option # 2 I will be a bit under 30k into this boat all together, and that is as high as I am willing to go. I do not plan on this being my "forever" boat, as the years go on my wife and i realize we like taking ling and slow trips, so i do think we will be going to more of a trawler type diesel engine boat. I do see myself keeping this for about 3 more years, than we will move on to something else.

                  Honestly hp for top end speed is not at all what i am going for, I generally cruise around 23-24 mph, but i figure if i can do that at a lower rpm, i would be better off
                  1998 bayliner 2355
                  mercruiser 5.7
                  alpha one

                  Comment


                    #12
                    Originally posted by 2850Bounty View Post





                    That's right.
                    There is no longer a push rod port nor a usable mounting location for the mechanical fuel pump.
                    Very easy to add!




                    Correct!
                    The only things gained by the Vortec cylinder heads are the swirl points (at the quench surfaces), and the larger intake runners.
                    The swirl points do ZERO when used with the GM Full Dished pistons.





                    Click image for larger version Name:	Quench and Squish area for Vortec SBC .jpg Views:	0 Size:	352.9 KB ID:	556893
                    This image may better explain the the Quench Effect area.

                    Note the black dotted lines indicating the piston's dished area.
                    The dished area on the left side comes up underneath the cylinder head's quench surface.
                    The dished area on the right side is underneath the combustion chamber area ONLY!



                    Click image for larger version Name:	Quench and Squish area explained 4.jpg Views:	0 Size:	121.2 KB ID:	556894
                    Rick can you explain how allowing some of the air fuel mix a place to hide, causes detonation? I have a thought on that, but am curious to what the theory is in explaining this.
                    I have always used 93 octane in our boat because that is all the local fuel docks sell and have never had any problems with detonation or pinging in all the years I have had this boat with the generic full dished pistons. I have had it set at 6*BTDC and am still running the standard mechanical advance Prestolite points distributor. For reasons I guess are specific to the 4.3 V6 the advance curve for this engine, is a lot less aggressive than that for the V8s, according to the charts I have this engine is limited to a total timing advance of 18* at 3200 rpm (12* full advance + 6* base timing) while the 5.0 got 10* base plus 12* full advance at the same rpm for a total of 22*, and the 5.7 got a base of 8*, plus 21* full advance for a total of 29* at 3000 rpm.
                    88 Four Winns 200 Horizon 4.3 OMC
                    98 Jeep Grand Cherokee 4.0/Selectrac
                    07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

                    Long Island Sound Region

                    Comment


                      #13
                      88fourwinns, I’m snowmobiling this weekend, but will do so next week.
                      Rick E. 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

                      Comment


                        #14
                        Originally posted by 88fourwinns View Post

                        Rick can you explain how allowing some of the air fuel mix a place to hide, causes detonation? I have a thought on that, but am curious to what the theory is in explaining this.
                        I have always used 93 octane in our boat because that is all the local fuel docks sell and have never had any problems with detonation or pinging in all the years I have had this boat with the generic full dished pistons. I have had it set at 6*BTDC and am still running the standard mechanical advance Prestolite points distributor. For reasons I guess are specific to the 4.3 V6 the advance curve for this engine, is a lot less aggressive than that for the V8s, according to the charts I have this engine is limited to a total timing advance of 18* at 3200 rpm (12* full advance + 6* base timing) while the 5.0 got 10* base plus 12* full advance at the same rpm for a total of 22*, and the 5.7 got a base of 8*, plus 21* full advance for a total of 29* at 3000 rpm.
                        First of all...... Detonation and Pre-ignition are two entirely different phenomena, in which case neither of them are good.


                        The gasoline engine's compressed fuel/air does not explode...... it actually undergoes a "burn".
                        Because it undergoes a burn, there is a duration to it.
                        Since there is a duration to it, we need to start the fuel/air ignition prior to the piston being at TDC (unlike a diesel engine).
                        Since we vary engine RPM, the ignition event must also be varied as per RPM.
                        The primary goal is to achieve maximum fuel burn "expansion" at/near 12* to 14* ATDC, and at any given RPM.
                        Our other goal is to create one even burn without any secondary burns (i.e., detonation).

                        The SBC combustion chamber is wedge shaped.
                        To the north of the chamber is a quench surface (also known as a squish area or surface).


                        Click image for larger version  Name:	SBC wedge shaped combustion chamber.jpg Views:	0 Size:	60.9 KB ID:	557279
                        The GM full dished piston places a portion of the dished area directly underneath the quench surface.
                        With this design, there is no effect means of forcing all of the combustible gasses out into the main combustion chamber, of which creates a potential for detonation.



                        On the left side below, I show a GM full dished piston.
                        Note the dotted lines that indicate where the piston's dished area would be.

                        On the right side, I show how a proper piston profile works in harmony with the quench surface!
                        Note the dotted lines that indicate where the dished area would be.


                        Image result for wedge shaped combustion chamber"


                        Bottom line.... the area created by the GM full dished piston (specifically underneath the quench surface) makes for a detonation prone combustion chamber.
                        In order to prevent or reduce this potential, we hold back on ignition advance.
                        However, this also makes for a lazy LPCP (location of peak cylinder pressure.... i.e., 12* to 14* ATDC) of which makes for a less torque producing engine.



                        GM knows this, and you will not find the Full Dished piston being used in their performance SBCs.
                        GM and most re-builders use the F/D piston because:
                        .... one part number fits all bores.
                        .... they are inexpensive.

                        Keep in mind that a proper Q/E build does not necessarily mean that you would be building a HP engine.
                        It actually means that you would be building a much better suited SBC Marine engine that will not be as prone to detonation.
                        Our Static Compression Ratio is controlled by the dish volume, so when a Q/E build is being organized, the piston dish volume will be determined and ordered.
                        It's as easy as if falling out of a tree.

                        .
                        Rick E. 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

                        Comment


                          #15
                          So it is the air/fuel mix hiding under the quench surface, that creates secondary burns, that can cause detonation, correct?
                          Is it then correct to say that the full dished piston design makes the engine susceptible to detonation but not necessarily pre-ignition (pinging)?

                          the difference between pre-ignition and detonation as per Chrysler Corp circa 1954, a little hard to listen to but informative!

                          https://www.bing.com/videos/search?q...6FORM%3DHDRSC3

                          https://www.bing.com/videos/search?q...7&&FORM=VDRVRV

                          from ethyl corp same era interesting videos of what actually happens inside the engine during detonation.
                          88 Four Winns 200 Horizon 4.3 OMC
                          98 Jeep Grand Cherokee 4.0/Selectrac
                          07 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

                          Long Island Sound Region

                          Comment

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