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    #46
    Yes, I have thought about it... several times. but still havent done it.
    I have also been meaning to check and see how the cav plate on the outdrive aligns with the bottom of the hull when the drive is fully down, but havent done that either... I have been running with the drive in the full down position, and I got to thinking if my outdrive lowers to the point where the cav plate is plowing a little water, this could be holding me back slightly... it would be giving me stern lift at the same time, but that is what the tabs are for... I could trim the outdrive and adjust the tabs as needed IF I find they are out of plane with one another...


    NU LIBERTE'
    Salem, OR

    1989 Bayliner 2556 Convertible
    5.7 OMC Cobra - 15.5x11 prop
    N2K equipped throughout..
    2014 Ram 3500 crew cab, 6.7 Cummins
    2007 M-3705 SLC weekend warrior, 5th wheel
    '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
    Heavy Equipment Repair and Specialty Welding

    Comment


      #47
      OMC 460 was coupled to a King Cobra & was available in gear ratio 1.33:1 only I believe.
      post a pic of your lower...we can verify.
      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


        #48
        Originally posted by Ruffryder View Post
        OMC 460 was coupled to a King Cobra & was available in gear ratio 1.33:1 only I believe.
        post a pic of your lower...we can verify.
        I will try to get to that... I dont know how to tell the difference, other than I believe the king cobra had markings on the tilt rams.... the transom shield and rams are original, but the outdrive itself is different, as its easy to tell because the transom shield and rams have serious pitting/erosion issues, but the outdrive is in good condition...


        NU LIBERTE'
        Salem, OR

        1989 Bayliner 2556 Convertible
        5.7 OMC Cobra - 15.5x11 prop
        N2K equipped throughout..
        2014 Ram 3500 crew cab, 6.7 Cummins
        2007 M-3705 SLC weekend warrior, 5th wheel
        '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
        Heavy Equipment Repair and Specialty Welding

        Comment


          #49
          Originally posted by Solandri View Post
          Yes I did consider the 2859. I actually liked the layout of it better, but I crossed it off the list because it only has a 15 degree deadrise angle (the 2556 is 18.5 deg). I didn't feel that was sufficient for taking the boat as far offshore as I wanted. (The 2855 has 21.5 deg I believe, but it really hurts fuel economy and the cockpit seemed too small.)
          In the B2556 the angle on the transom is not less than is 21.5 - 22 deg

          Comment


          #50
          Originally posted by Centerline2 View Post

          I will try to get to that... I dont know how to tell the difference, other than I believe the king cobra had markings on the tilt rams.... the transom shield and rams are original, but the outdrive itself is different, as its easy to tell because the transom shield and rams have serious pitting/erosion issues, but the outdrive is in good condition...
          On my B2556 1989 the OMC Cobra 1989 drive is installed №985689 with a gear ratio of 1.41: 1

          Comment


          • builderdude
            builderdude commented
            Editing a comment
            Maxim, post pic of ya boat

          #51
          Originally posted by Maxim_23 View Post

          In the B2556 the angle on the transom is not less than is 21.5 - 22 deg
          Here are the specs for the 2556.
          Click image for larger version

Name:	image.png
Views:	1
Size:	1.30 MB
ID:	415502
          Dave
          Edmonds, WA
          "THE FIX"
          '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
          (.030 over-Vortec top end-part closed cooled)
          The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
          Misc. projects thread
          https://www.baylinerownersclub.org/f...56-gctid789773

          Comment


            #52
            Originally posted by builderdude View Post

            Here are the specs for the 2556.
            Click image for larger version  Name:	image.png Views:	1 Size:	1.30 MB ID:	415502
            also believed, until he measured
            https://yadi.sk/i/LoAd0sPc3SyqKL
            I do not know how to insert files. I give links to the disk

            Comment


              #53
              Photo when buying a boat. Before moving

              Comment


              • Solandri
                Solandri commented
                Editing a comment
                I'd actually been wondering about that. I'm pretty good at estimating angles and when eyeballing my 2556, the deadrise angle looked to be more than the 18.5 deg in the specs. But since I'd already bought the boat by the time I took a good look at it, it was a moot point - I was stuck with it regardless of what the exact angle was. So I never bothered to actually measure it.

                One thought that did occur to me - do you see that stepped chine directly above the "4" in your diagram, to the left of the trim tab? I'm curious if maybe the angle between the keel to the right edge of that chine is 18.5 degrees. Deep-V hulls like a 22 degree deadrise have a tendency to roll a lot in waves. The purpose of that chine is to resist that rolling motion. So I'm guessing Bayliner's marketing opted to measure the angle from the keel to the edge of that chine. That way they could market the boat as being more stable than people would think a 22 degree deadrise boat would be. It's just one of those situations where a single number can't really describe the boat's performance.

                Regardless of 18.5 or 22 degrees on the 2556, the 15 degrees on the 2859 seemed completely inadequate for where I wanted to take the boat (Channel Islands off Southern California - 25 to 75 miles offshore).

              #54
              Originally posted by Maxim_23 View Post

              On my B2556 1989 the OMC Cobra 1989 drive is installed №985689 with a gear ratio of 1.41: 1

              Comment


                #55
                Originally posted by Maxim_23 View Post
                Photo when buying a boat. Before moving
                Deadrise is just a term that can be confusing, and is nearly as hard to describe.... on a boat, deadrise is measured in relation to the keel.

                "transom" deadrise can mean the angle of the transom, or transom angle/rake, measured FROM 90 degress vertical of the keel....
                "hull" deadrise is the angle of the hull from the keel to the chine, FROM horizontal... or height of the chine above the keel line, measured in degrees. the hull deadrise can change from to front of the boat to the rear.

                commonly, the transom deadrise is the wording most often seen, so unless its specified which measurement it is, assume its the hull deadrise measured at the transom.

                properly, the deadrise measurement should always include which measurement is being referred to...



                NU LIBERTE'
                Salem, OR

                1989 Bayliner 2556 Convertible
                5.7 OMC Cobra - 15.5x11 prop
                N2K equipped throughout..
                2014 Ram 3500 crew cab, 6.7 Cummins
                2007 M-3705 SLC weekend warrior, 5th wheel
                '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
                Heavy Equipment Repair and Specialty Welding

                Comment


                • Solandri
                  Solandri commented
                  Editing a comment
                  The deadrise angle of the transom itself is pretty meaningless since it has almost no impact on performance (it affects boat handling in following seas). So when people talk about the transom deadrise angle, they're almost always talking about the hull's deadrise angle measured at the transom. That affects how smoothly the boat can cut through chop and swells.

                  I agree with you that people (and boat manufacturers) should be clearer about this. But unless they give more than one deadrise angle, I just assume it's the hull deadrise measured at the transom. Since that's the one that generally has the biggest impact on performance and is of the most interest to most people. (Bow deadrise can be important too.)

                #56
                Originally posted by Centerline2 View Post

                all boats will be a bit different depending on how they are set up and with what engine, outdrive and prop.... AND how well the boat is balanced and trimmed with how much load they carry... but around 2mpg is about normal when set up right... even when set up perfectly, the actual speed at one runs makes a huge difference in mpg.

                my 2556 is considered to be heavily loaded, and when I had a 13p prop on my Cobra outdrive behind a stock 5.7, i was getting about 1.2mpg when on plane, no matter the speed.... but I was over propped and could only make 4200rpm and was running about 20-21mph...... but then at about 1000rpm/5-6mph, the meter would show a steady 5.5mpg....

                this past weekend was the first time Ive been out since changing to a 11P PROP.... now I can make 24.5 mph @ 4500rpm, and the meter shows 2.3mpg at 3500 to 4000rpm... I didnt check it at wot, or at lower speeds, but its nearly twice as efficient with the right prop on it for the gearing it has...., of which im not exactly sure of because the outdrive has been changed at some time in the past.

                I think I have a higher geared outdrive than comes stock behind a 5.7, and that is why my prop is only an 11P (or maybe its because im loaded so heavy).... i think a 10P would give the extra 1500rpm I would like to be able to make..

                but with all this said, I can STILL find an operating speed where my fuel burn rate is less than a mile per gallon.... which is why its nice to have the meters/gauges to show you instantly where the sweet spots are in the operating range....

                if you can get 2mpg at 3500-4000 rpm, which is cruise speed, you are close to as good as it gets...
                Thank you for your answer. That is amazing to gain almost double mpg with a prop change. Wow
                I've been obsessed with 2556 for over a year I've been researching about it. I am in loved with 2556. The only problem is range and mpg because during summer almost every weekend I go to Catalina island 30 mi one way sometimes San Clemente island 67 mi one way. Add to that trolling for tuna and moving around the island. Just a short trip going to Catalina and fishing around the island usually about 80 nmi.
                My average trips summer time especially when tuna moves in are between 80-140 nmi.
                2556 that I am looking at has 7.4 big block with Bravo 2. I've heard that with that set up I can get at best 1.3-1.5 mpg

                Comment


                  #57
                  Originally posted by vladafizio View Post

                  Thank you for your answer. That is amazing to gain almost double mpg with a prop change. Wow
                  I've been obsessed with 2556 for over a year I've been researching about it. I am in loved with 2556. The only problem is range and mpg because during summer almost every weekend I go to Catalina island 30 mi one way sometimes San Clemente island 67 mi one way. Add to that trolling for tuna and moving around the island. Just a short trip going to Catalina and fishing around the island usually about 80 nmi.
                  My average trips summer time especially when tuna moves in are between 80-140 nmi.
                  2556 that I am looking at has 7.4 big block with Bravo 2. I've heard that with that set up I can get at best 1.3-1.5 mpg
                  I would think even with the 454 you could do a little better than 1.5mpg....what is your top rpm that you can make with the prop you have?... at what speed? if you are over propped, which is common, the engine is always working harder than it should be. if you cant reach the upper end of the operating range, you are over propped, especially for offshore work...

                  all other things being equal (except for the prop), an engine that is propped so it can run along easy at 4600rpm will burn a substantial amount less fuel than the same engine, over propped, running hard to maintain 43-4600 rpm... also, when the pitch is right so the engine isnt laboring hard all the time to maintain its maximum rpm, and then the rpm is reduced to 32-3500 (cruise speed), the boat runs along easier and with even better economy...


                  NU LIBERTE'
                  Salem, OR

                  1989 Bayliner 2556 Convertible
                  5.7 OMC Cobra - 15.5x11 prop
                  N2K equipped throughout..
                  2014 Ram 3500 crew cab, 6.7 Cummins
                  2007 M-3705 SLC weekend warrior, 5th wheel
                  '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
                  Heavy Equipment Repair and Specialty Welding

                  Comment


                    #58
                    Originally posted by vladafizio View Post
                    Wow
                    I've been obsessed with 2556 for over a year
                    Me too, it's a sickness...
                    Dave
                    Edmonds, WA
                    "THE FIX"
                    '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                    (.030 over-Vortec top end-part closed cooled)
                    The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                    Misc. projects thread
                    https://www.baylinerownersclub.org/f...56-gctid789773

                    Comment


                      #59
                      Originally posted by Centerline2 View Post
                      all other things being equal (except for the prop), an engine that is propped so it can run along easy at 4600rpm will burn a substantial amount less fuel than the same engine, over propped, running hard to maintain 43-4600 rpm... also, when the pitch is right so the engine isnt laboring hard all the time to maintain its maximum rpm, and then the rpm is reduced to 32-3500 (cruise speed), the boat runs along easier and with even better economy...
                      It's actually a bit more complicated than that.

                      The engine has a certain horsepower curve. As RPM increases, so does horsepower, up to a certain RPM beyond which power begins to drop. (And if you're curious what the torque curve tells you, power = torque * RPM. Or put another way, power is the engine's output per unit time. Torque is the engine's output per revolution.)


                      The water resistance of the boat increases with speed, but not linearly, and not even constantly for a planing hull.


                      The simplistic situation you're describing would happen if the HP curve exactly matched the resistance curve. Since the two don't match, you're left with a choice. At which speed do you want to optimize performance?
                      • If you want the highest possible top speed, you want to to align the peak of the HP curve with the resistance curve (find where the two are equal), then find the speed at which that resistance occurs, and select a prop pitch which (with slippage) will give you that speed.
                      • If you want the best mileage, you want to find the RPM at which the engine operates most efficiently - produces the most HP per GPH of fuel. Take the HP at that RPM, align it with the resistance curve to find the speed at which that resistance occurs, and select a prop pitch which (with slippage) will give you that speed.

                      Your explanation implies that the engine can be overburdened only if you're over-propped. While that's the most common case, it's not the only way this can happen. For a planing hull, in both the above cases you also need to make sure the engine's HP at the speed at which the boat begins to plane exceeds the hump resistance (i.e. engine produces the power needed to get the boat up to plane). This is harder to achieve in the first case (propped for top max speed). Since the peak HP will fall at a higher speed in that case, the engine will be at a lower RPM (and thus producing less HP) when it's trying to get over the hump. But even if you've propped for best efficiency, you can still overload the boat so that the engine can't produce enough power to get up to plane. This is one of the reasons diesels tend to perform better - their HP curve is more balanced with the peak towards the middle and plenty of power at lower RPMs, unlike a gas engine's power curve which is skewed towards high RPM. The tradeoff of course is that diesels wind up with lower top speeds since the HP does not ramp up with RPM as much.

                      So this isn't a case where there's a single "correct" prop pitch for your boat. The correct pitch varies with engine RPM (whatever pitch is needed to make the HP curve align with the resistance curve at all speeds/RPMs). But since we're not using variable pitch propellers, we're forced to select a single point on the HP curve around which we want to optimize - max speed or best fuel efficiency. (If the engine is too small for the boat, you may even be forced to optimize to make sure there's enough power to get the boat up to plane.)
                      1994 2556, 350 MAG MPI Horizon, Bravo 2

                      Comment


                        #60
                        Originally posted by Solandri View Post
                        It's actually a bit more complicated than that.

                        The engine has a certain horsepower curve. As RPM increases, so does horsepower, up to a certain RPM beyond which power begins to drop. (And if you're curious what the torque curve tells you, power = torque * RPM. Or put another way, power is the engine's output per unit time. Torque is the engine's output per revolution.)


                        The water resistance of the boat increases with speed, but not linearly, and not even constantly for a planing hull.


                        The simplistic situation you're describing would happen if the HP curve exactly matched the resistance curve. Since the two don't match, you're left with a choice. At which speed do you want to optimize performance?
                        • If you want the highest possible top speed, you want to to align the peak of the HP curve with the resistance curve (find where the two are equal), then find the speed at which that resistance occurs, and select a prop pitch which (with slippage) will give you that speed.
                        • If you want the best mileage, you want to find the RPM at which the engine operates most efficiently - produces the most HP per GPH of fuel. Take the HP at that RPM, align it with the resistance curve to find the speed at which that resistance occurs, and select a prop pitch which (with slippage) will give you that speed.

                        Your explanation implies that the engine can be overburdened only if you're over-propped. While that's the most common case, it's not the only way this can happen. For a planing hull, in both the above cases you also need to make sure the engine's HP at the speed at which the boat begins to plane exceeds the hump resistance (i.e. engine produces the power needed to get the boat up to plane). This is harder to achieve in the first case (propped for top max speed). Since the peak HP will fall at a higher speed in that case, the engine will be at a lower RPM (and thus producing less HP) when it's trying to get over the hump. But even if you've propped for best efficiency, you can still overload the boat so that the engine can't produce enough power to get up to plane. This is one of the reasons diesels tend to perform better - their HP curve is more balanced with the peak towards the middle and plenty of power at lower RPMs, unlike a gas engine's power curve which is skewed towards high RPM. The tradeoff of course is that diesels wind up with lower top speeds since the HP does not ramp up with RPM as much.

                        So this isn't a case where there's a single "correct" prop pitch for your boat. The correct pitch varies with engine RPM (whatever pitch is needed to make the HP curve align with the resistance curve at all speeds/RPMs). But since we're not using variable pitch propellers, we're forced to select a single point on the HP curve around which we want to optimize - max speed or best fuel efficiency. (If the engine is too small for the boat, you may even be forced to optimize to make sure there's enough power to get the boat up to plane.)

                        you are correct. and while I dont disagree with with you describe, its beyond the context of what I wrote..... some of what you describe is determined by the build of the engine. and as we dont know for certain, one can only assume the engine is OEM built as a marine engine for the boat that its in.... any custom cams, pistons, jetting, or other performance mods that someone can think up, can change things dramatically and not always for the better. but the limiting factor of the OEM marine engine is the recommended rpm, and in a boat this is adjusted by the prop...

                        so I will stand by my statement that ALL OTHER THINGS BEING EQUAL, an over propped engine will be less efficient and use more fuel than the engine will if its propped correctly....... in the same way that any boat that is propped correctly will burn more fuel to try and maintain its speed if its heavily loaded..... the RPM of an engine, in itself, is not the primary determining factor in the fuel consumption, but its the position of the throttle plate at that RPM that controls the fuel flow..... as does the internals of the engine, but the only thing that can be easily adjusted is the prop pitch, which in turn affects the rpm and power, which affects the efficiency.

                        YES, we may not know what cam is in the engine or what the torque and hp curves actually are, but STILL, an running an engine "easily" at any given rpm (within the range that it was built for) will be more efficient than when heavily burdened and working hard at the same rpm....





                        NU LIBERTE'
                        Salem, OR

                        1989 Bayliner 2556 Convertible
                        5.7 OMC Cobra - 15.5x11 prop
                        N2K equipped throughout..
                        2014 Ram 3500 crew cab, 6.7 Cummins
                        2007 M-3705 SLC weekend warrior, 5th wheel
                        '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
                        Heavy Equipment Repair and Specialty Welding

                        Comment

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