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can we get 250hp from a 200hp Mercruiser 4.5L?-gctid804882

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    can we get 250hp from a 200hp Mercruiser 4.5L?-gctid804882

    just left the boatshow with some strange information. I told the Bayliner salesman I wouldn't mind the 250hp 4.5L and he said there is no difference between the 200hp and 250hp. The 200hp's computer module will push the engine to 250hp to get the boat on plane then settle back to 200hp. I never heard such a thing before on any engine, but since he may end up being my dealer for a new VR5 would like some more info on the 'new' Merc 4.5L, anyone else know how the computers work on these engines?

    #2
    I've sure like to be able to verify if that is true. I've been wondering/asking if there is a conversion available to take the 200 to 250.

    Certainly wouldn't hurt my feelings to give it a quicker hole shot.

    Comment


      #3
      The guy's been smoking tough,

      the biggest BS I've heard this year...
      Joon, Kathy, Jaden & Tristan
      Uniflite 42 AC, DD 671N
      93 3058 sold
      92 2855 (day boat)
      91 Fourwinns 205 (lake boat)
      Longbranch WA
      Life is Good

      Comment


        #4
        Getting up on plane is as much about thrust / toque as it is HP. That is why a 4 blade prop will give you a better hole shot, more thrust.

        Variable HP. OK, how does the boat know you are trying to get up on step and therefore increase the HP?

        Here is the deal, Mercury has been very, very tight lipped about the 4.5 so there are so many "theories" as to the engine. Some claim it is just a 4.3 stroked. Some claim it is a 6.0 with 2 cylinder's chopped off. Who knows for sure about the block. Some things are for certain, the intake and fuel delivery systems are not off the shelf. They have been purposely designed along with service points that make sense for a marine engine.

        When it comes to engines you never hear someone saying they wish they had gone with a smaller engine package for their boat. Could there be a chip out there someday for the 4.5 200HP to increase HP and torque, perhaps. Small market may drive the cost so high that it may not be worth making.
        Phil, Vicky, Ashleigh & Sydney
        1998 3055 Ciera
        (yes, a 1998)
        Previous boat: 1993 3055
        Dream boat: 70' Azimut or Astondoa 72
        Sea Doo XP
        Sea Doo GTI SE
        Life is short. Boats are cool.
        The family that plays together stays together.
        Vice Commodore: Bellevue Yacht Club

        Comment


          #5
          There is an after market fuel remapping chip for both 200 / 250 already...
          Joon, Kathy, Jaden & Tristan
          Uniflite 42 AC, DD 671N
          93 3058 sold
          92 2855 (day boat)
          91 Fourwinns 205 (lake boat)
          Longbranch WA
          Life is Good

          Comment


            #6
            Your gonna get close with a 4.3L hp wise, way less expensive for parts, they have made the 4.3 l engine for a very, very, long time.

            Do a comparison for say a mani or any other part.

            Oh by the way who knows how to work on a 4.5l ?

            4.3 is a snap in my opinion the best 6 cylinder ever designed.

            You want to boat and enjoy yourself or have your boat in the shop all the time.
            Be good, be happy, for tomorrow is promised to no man !

            1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

            '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

            Manalapan N.J

            Comment


              #7
              "just left the boatshow with some strange information. I told the Bayliner salesman I wouldn't mind the 250hp 4.5L and he said there is no difference between the 200hp and 250hp. The 200hp's computer module will push the engine to 250hp to get the boat on plane then settle back to 200hp"

              I have heard all kinds of things at boat shows over the years...

              One method we adopted to clear up some of these is to simple ask the salesman/dealer to just put it on the quote.

              Yes - just put down in writing exactly what is said above guaranteeing that the boat will be delivered as promised and as described.

              I predict there will be a brief pause - then a very in unique/creative and unusual reason why they cannot memorialize their claims in writing.

              Then we end up pondering this , if they distorted one item about the boat/deal how many other items are also distorted?
              Northport NY

              Comment


                #8
                "dicko" post=804882 wrote:
                just left the boatshow with some strange information. I told the Bayliner salesman I wouldn't mind the 250hp 4.5L and he said there is no difference between the 200hp and 250hp. The 200hp's computer module will push the engine to 250hp to get the boat on plane then settle back to 200hp. I never heard such a thing before on any engine, but since he may end up being my dealer for a new VR5 would like some more info on the 'new' Merc 4.5L, anyone else know how the computers work on these engines?
                Maybe, maybe not.... As Chief Allen stated, a way to find out would be to check for part number differences on key components: ECU, Intake manifold, camshaft, pistons, heads, etc. Even if the only difference is the ECU, would Mercury sell a 250 ECU not tagged for a particular engine s/n? For example, I have a Suzuki 20hp EFI outboard. Out of curiosity, I did a part number comparison with the 15hp outboard and found that the ECU was in fact the only different key component.

                As other mentioned, there are some aftermarket fuel curve re-mappers available already. These devices basically trick the ECU into changing the air/fuel ratio and/or ignition timing at various points. I am very familiar with doing this on motorcycles and it takes some dyno time to get it right. Have these aftermarket outfits put the engines on a dyno and optimized the fuel/air and ignition timing or are they doing it by seat of the pants?
                1999 3788, Cummins 270 "Freedom"
                2013 Boston Whaler 130 SS
                Anacortes, WA
                Isla Verde, PR

                Comment


                  #9
                  Mercruiser is known to do this to their engines, all pretty much the same engine...

                  Mercury 4 stroke EFI 75, 90, 115 HP

                  Mercruiser 357 A4V 285HP, 357 B4V 320HP

                  Mercruiser 4.5 200HP, 4.5 250HP
                  Joon, Kathy, Jaden & Tristan
                  Uniflite 42 AC, DD 671N
                  93 3058 sold
                  92 2855 (day boat)
                  91 Fourwinns 205 (lake boat)
                  Longbranch WA
                  Life is Good

                  Comment


                    #10
                    "Ruffryder" post=805225 wrote:
                    Mercruiser is known to do this to their engines, all pretty much the same engine...

                    Mercury 4 stroke EFI 75, 90, 115 HP

                    Mercruiser 357 A4V 285HP, 357 B4V 320HP

                    Mercruiser 4.5 200HP, 4.5 250HP
                    Do you know if the differences are ECU programming alone, or if other internal components are changed?
                    1999 3788, Cummins 270 "Freedom"
                    2013 Boston Whaler 130 SS
                    Anacortes, WA
                    Isla Verde, PR

                    Comment


                      #11
                      Same bore & stroke, same tuned scroll intake, same digital inductive ignition,

                      So the differences are ECM programming alone, but that is strictly just my opinion since I haven't tear down these 2 motors side by side yet
                      Joon, Kathy, Jaden & Tristan
                      Uniflite 42 AC, DD 671N
                      93 3058 sold
                      92 2855 (day boat)
                      91 Fourwinns 205 (lake boat)
                      Longbranch WA
                      Life is Good

                      Comment


                        #12
                        You probably don't need a teardown. Some time with the parts manuals will reveal the answer. As a matter of fact, if Mercury already has long or short block P/Ns that's all that is needed for the comparison.
                        1999 3788, Cummins 270 "Freedom"
                        2013 Boston Whaler 130 SS
                        Anacortes, WA
                        Isla Verde, PR

                        Comment


                          #13
                          The ECM is very likely not the difference.

                          There are three options I can think of. Of those, only one makes sense:

                          1) Detuned timing (reduced advance)

                          2) Lower compression

                          3) Different intake

                          #3, the different intake, is the normal route that manufacturers use to detune performance.

                          #1 is the only one you could change on the fly, but really it would just be creating a less efficient engine...unlikely that they would do this.

                          With a gasoline engine, you need to match the mass of the air with the correct amount of fuel (Within an air fuel ratio band, but pretty tightly controlled). Because of this, the typical way to detune an engine is to reduce the airflow, not ecm programming.

                          Chay

                          Comment


                            #14
                            Wait, I have to contradict myself.

                            If the engine has variable valve timing/lift the ECM could control airflow and therefore hp.

                            It probably does, being a new engine, perhaps that's how it's done.

                            Chay

                            Comment


                              #15
                              Nope no variable valve timing.

                              & Intake is exactly the same between these 2 engines.

                              https://www.perfprotech.com/mercury-...0?umodel=20119

                              "On new generation fuel injected engines you are not able to adjust the Air to Fuel Ratio in order to add more power output with re-jetting, like on carbureted models.

                              Typical performance tuner device wires inline with the signal wire of Intake Air Temperature (IAT) sensor

                              This fuel injection remap is designed to fool the ECU thinking the intake air much more cooler, then the Electronic Engine Management will send more fuel for a richer mix, "

                              Not by reducing or adding airflow...

                              On a Porsche 580 HP engine, HP difference fluctuation can be up to 80 horses hot day driving VS cool night.
                              Joon, Kathy, Jaden & Tristan
                              Uniflite 42 AC, DD 671N
                              93 3058 sold
                              92 2855 (day boat)
                              91 Fourwinns 205 (lake boat)
                              Longbranch WA
                              Life is Good

                              Comment

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