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What cruise and Top Speed do you run in your 28'

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  • What cruise and Top Speed do you run in your 28'

    To All 28' Owners.

    Would you mind sharing your normal cruise speed, RPM and Top Speed RPM?
    Ocean Fury is powered with twin Volvo TAMD31 Turbo Diesels @ 150 HP Each.
    My Normal cruise speed is about 12 knots at 3200 RPM. Just barely on a plane.
    Tops speed is 18 knots at 3700-3800 RPM.

    Wish I could get to a cruise speed of about 14-15 knots. Any ideas?

    Thanks,
    Wally
    Ocean Fury

  • #2
    Wally

    Depending on the condition of you bottom (clean.no barnacles, weeds etc.) 12 knots may be max. Try running it up to WOT, with the best trim you can get, then back off the throttles slowly to a point where you begin to fall off plane. 100 or 200 rpm past that may be the best cruise setting.
    The cruise liner QE2 moves only six inches for each gallon of diesel fuel that it burns.

    1982 28' Long Cabin "Molly Brown" sweating through a long hot summer. Massive California forest fires fill our sky with smoke. SUP paddlers and kayakers transit the harbor with abandon, thinking they have the right of way over all boats.

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    • #3
      Are you running v-drives or outdrives? You may need to consider a prop change. As I’m sure you are aware of the tamd31’s 150hp would not have been original to the boat, should be early to mid 90’s production years. Not too many 4cyl diesels here on the forum to compare with except Glasshawk, and he is pushing 240hp? I think. I personally would say those numbers are a bit low for a twin engine diesel. It may take a little reasearch but I’d start with a prop calculator to get a base line idea of what you need. I’d also start looking at gear ratios for the drives or trans and see if they are within spec since it would seem the diesels were a upgrade at some point. And last not saying it’s true but just how tired are the motors, injectors or maybe a little easier the turbos. Just a few ideas to check. My 28 non fly ridge with twin 250hp 5.7 v8 gassers and Merc alpha 1 drives are in the mid 20’s if I remember right and tops around 32.

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      • #4
        When I ran the Crusader 350/310hp engines on V-drives cruise speed was 22/23mph at 3000 and top speed was 37/38mph @ 4500. Since installing the new 383/350hp engines and not re-propping to utilize the increased power cruise speed is virtually the same although fuel flow is shows an improvement. Top speed is 42mph at 5200 and engines were still climbing in RPM, I just chickened out. I hope to add bigger props soon.
        "Joint Venture" 1978 28' twin 2017 Vortec roller cam 383/6.3L 350hp engines - You name it, I've either replaced it, restored it, rebuilt it or repaired it. That's my job now that I'm retired.

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        • #5
          Thanks for the input!

          Comment


          • #6
            Running V-drives.
            Clean hull.
            450 Hours on both.

            Looks like you had 500HP to my 300HP. Maybe my numbers are about right?

            Thanks for the input.

            Comment


            • #7
              Wow Bill, that is one fast boat!
              700 HP vs my 300... Big difference.

              How does the boat "feel" at 35+ MPH?

              Comment


              • #8
                one thing to remember is torque is what pushes a boat, not so much the hp. i would be looking for more pitch if i was you. with the 4bt cummins in my 23' i now can pull 28knt at 2800 rpm. that is with 140hp
                1980 2400 Cuddy I/O, 2017 Cummins 4BT coupled to a Volvo DP-SM with F9 Props, and a 2014 Mercury 15HP Pro-Kicker "LOOSE CHANGE"

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                • #9
                  Originally posted by wally View Post
                  Wow Bill, that is one fast boat!
                  700 HP vs my 300... Big difference.

                  How does the boat "feel" at 35+ MPH?
                  What Dave says about torque is very true. My 700hp produces about 800ft.lbs. of torque. Your 300hp produces somewhere around 450-500ft.lbs. of torque. You probably need more pitch in your props. What gear ratio V-drives are you running. There's a tag on side of transmission that tells you. What are your existing props. Your boat probably left the factory as a gas powered boat with the Volvo's installed in a repower. Could be the props were never changed.

                  At 30+ you don't play with trim tabs very much, at 35+ NEVER play with trim tabs unless you want to see how it feels when a 28 hull falls over on it's side. A real thrill.
                  "Joint Venture" 1978 28' twin 2017 Vortec roller cam 383/6.3L 350hp engines - You name it, I've either replaced it, restored it, rebuilt it or repaired it. That's my job now that I'm retired.

                  Comment


                  • #10
                    Had a dash plaque made for my Firebird Formula: ‘Do Not Lower Windows at Speeds in Excess of 155 MPH’. Joint Venture needs a dash plaque: ‘Do Not Touch Trim Tab Controls at speeds in excess of 35 MPH’. Sit down, hang on and shut up!
                    The cruise liner QE2 moves only six inches for each gallon of diesel fuel that it burns.

                    1982 28' Long Cabin "Molly Brown" sweating through a long hot summer. Massive California forest fires fill our sky with smoke. SUP paddlers and kayakers transit the harbor with abandon, thinking they have the right of way over all boats.

                    Comment


                    • #11
                      Great Info everyone. Thank you for the input.

                      The props are 3 blade 17x16. Any idea what kind of pitch would be optimal? Ill check on the gear ratio. Do you happen to know what would be best?

                      Again, thanks. I really appreciate the information.

                      Wally

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                      • #12
                        Wally

                        Compare the engine specs for WOT or even better, specs for maximum torque/HP RPM.
                        Compare those numbers observed underway. If your existing WOT performance is close to your engine specs. then pthe props may be correct . If there is a big difference, you can adjust up or down with RE pitching.
                        The cruise liner QE2 moves only six inches for each gallon of diesel fuel that it burns.

                        1982 28' Long Cabin "Molly Brown" sweating through a long hot summer. Massive California forest fires fill our sky with smoke. SUP paddlers and kayakers transit the harbor with abandon, thinking they have the right of way over all boats.

                        Comment


                        • #13
                          WOT looks to be within 100 RPM. I can run at 3700-3800RPM.

                          Do you believe that larger trim tabs might help? The trims on it seem fairly small.

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                          • #14
                            If you trim all the way bow down do you go faster than with only a little bow down trim? If not then I don't think larger tabs will increase top speed-maybe help with getting on plane but after that probably not.

                            Edit: previous boats I've had all went their fastest with no trim tabs deployed, but none of them were a 28 gp... haha.

                            Comment


                            • #15
                              Thanks to everyone on your input.
                              Well, I "thought' Ocean Fury's bottom was clean... Had it cleaned/dived. Made a nice weeks run to the San Juan's. What a difference a hull cleaning makes! Cruise easy at 13-15 knots. Ran up to 4k max at 22.5 Knots! 8.5 GPH and purred.

                              Love this old Glasply!

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