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350 MAG Bravo 1 Performance Issue?

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  • #31
    Originally posted by Joesolta View Post
    QBhoy my Mercruiser manual says 4800-5200 for this engine. I haven't looked (yet), but it's probably roller lifters so they give it an extra few rpm. Although I get 5100 with a light-ish load, it's probably closer to 4900-5000 heavy, so that should be good.

    Achris, I have both an analog tach (set for 8 cyl) and the Mercruiser digital display fed from the ECM so the rpm is accurate.

    Thanks guys, I think that the average of the various opinions is that the numbers I have are not unexpected for this type of boat. Although, it's only 22.5 ft, the weight and high windage for it's size are limiting factors. I will try a slightly larger diameter prop to try to get the slip down. A lower angle of attack should improve efficiency a bit.
    Hi joesolta

    im 99% sure your engine is 4600-5000 rated. It says so in the manual I have and everywhere else I’ve looked. Are you defo looking at the specs for the right engine ?

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    • #32
      I have the Turning Point 4 blade stainless and have really been impressed with it. I had a stainless 3 blade before.
      83 Sunrunner 16.5 120 merc Alpha 1 drive SOLD 8/1/13

      1996 Crownline 202BR
      5.7l EFI 0f791070
      Bravo I drive

      GMC Yukon tow rig

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      • #33
        As mentioned, 200 extra rpm,s is no big deal. That ECM has a rev limiter also, so maybe his tack is off a bit.
        1999 Powerquest 260 legend
        502 mpi
        B1

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        • #34
          Specs for SBC 2001- up. 350 Mag MPI 4600-5000rpm. (See below) I'd be happy with it at 5100. Prop it down a little and the bottom end will suffer. Hole-shot will suffer, driveability will suffer. Unless you are flat-out racing on dead smooth water, I always prop high. 100 over is my target. When you're up and down swells, or the breeze is in and you've got a sloppy trip home, you'll be more than glad of the lighter prop. Makes the boat significantly easier to drive.

          Click image for larger version

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          xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
          The world takes on a whole new perspective when viewed from 100’ below.
          1972 Bertram ‘Bahia Mar’ 20
          2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
          (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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          • #35
            Mercruiser manuals seems to be all over the map. This is an owners manual dated oct 2007. My engine is 2009.

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            • #36
              Originally posted by Joesolta View Post
              Mercruiser manuals seems to be all over the map. This is an owners manual dated oct 2007. My engine is 2009.
              I would go by your owner's manual... Also, it should also be on the engine cover. You'll have serial number, a bunch of other specs (Spark plugs and gap, etc) and the WOT recommended.... If that also says 4800-5200, then ignore us, go by that....

              Chris....
              xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
              The world takes on a whole new perspective when viewed from 100’ below.
              1972 Bertram ‘Bahia Mar’ 20
              2006 Mercruiser 4.3MPI (0W617679) w/Alpha One Gen II (0W829301)
              (Original - 1972 '165' In-line 6. Previous - 1994 4.3LX)


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              • #37
                That’s not your engine. Yours is a 350 mag mpi surely. Although to be fair. It’s usually only the mpi that is 300hp on the 5.7

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                • #38
                  No problem spinning the motor to 5100 or 5200.

                  The rotating assembly has no idea what induction system is on the motor
                  Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                  1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                  Past Boats
                  1970 Wooster Hellion - Merc 9.8
                  2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                  1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                  What’s behind you doesn’t matter.Enzo Ferrari

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                  • #39
                    Ok. So it seems the seacore model 350 mag mpi is for some reason rated at up to 5200 rpm. Weird. Only difference is it’s fresh water cooled and closed system.
                    If yours is closed cooling with internal cooling, i apologise. If it isn’t, it’s 4600-5000.
                    Mine is the latter and I can tell you that it hits the limiter below 5200 rpm for sure.

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                    • #40
                      Yes it's a Seacore which includes closed cooling, anodized castings and additional stainless hardware.....except it appears, for the steering swivel shaft (!) which is now slowly leaking!! I see this topic is thoroughly cover in the forum.

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                      • #41
                        Hi, new here and in-between boats right now, but if I can offer a little advice, I owned a HEAVY TRI, 18' with the 898 (198 HP) Merc in it and found out at the time , the only difference between the 198HP and the 228HP was a 4 brl carb and different intake. Switched mine over and performed better but the RPM rose a little high. Talked to an old prop guy (Rebuilding service) and instead of increasing pitch, he rolled a little more cup into the trailing edge of the blades. I picked up about 3 mph with only a 150 drop in RPM. Worked great. Something you might try.

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                        • #42
                          thanks nortexed, i will check to see if we have someone like that in the area

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                          • #43
                            Sign up today
                            I never see anything on here about cupping, so I did some Google and found an excellent article about it:

                            http://www.mercuryracing.com/prop-sc...t-4-blade-cup/

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