Announcement

Collapse
No announcement yet.

4087 rpm and speed data, and prop size

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    4087 rpm and speed data, and prop size

    I'm interested in wide open throttle rpm and speed for the 4087 with 330 cummins. Also prop size and boat configuration like how much canvas, weight, etc. for the data given. Also cruising speed and rpm would be cool. I seem to be about 400 RPM short of spec (2850 rpm) so I'm curious what others are getting and with what prop. thanks
    Last edited by Jim_Gandee; 09-06-2020, 08:45 PM.

    #2
    Max RPM with my props is 2450, on a good day that will give me around 21knts, calm seas etc. Best ever was 24.5knts with current in my favor. Over the years I have averaged 8.1 knots at 1100 rpm giving me a a GPH of just under 5gph for both engines. Don't always run that slow, but that's how it's averaged out over the years. Not sure of prop size, my iPhone notes took a dump a while back and lost that information. Mine is a 1996 with 1 3/4" shafts and 250 turbo Cummins.

    Machog
    1996 4087 Lazy Days
    2011 11’ West Marine Rib 350 Lazy Mac
    2011 Porsche Cayman
    2010 Lexus IS 250C
    2008 Honda Ridgeline

    Comment


      #3
      Rodeo, my 4087 tops out at 2850 rpm, but I never run that high for very long. I have

      Prop info on the boat. Will return on

      Friday and forward to you.

      I also will forward contact for a prop

      Shop in st Simons GA. THey do fine

      Work, hood turnaround and fair prices.

      Comment


        #4
        thank you so much

        Comment


          #5
          Picking this thread up... Of course my rpm gauges are off but my port gauge does read 28/2900 rpm (both port and starboard engine notes are matching and no vibration). I get to about 22knots. Have seen it with wind at stern get to just over 3000 rpm. Should I consider a re-prop to bring it down slightly in the rpm band? With a one inch pinch increase what can I expect for increase on knots? Will my cruise speed change any? Will this affect low speed fuel economy in theory better or worse? FYI, I don't run WOT often, more trawling around at 7-9knots. New to this so not sure if the sig works. boat is 1997 4087 250 cummins - 4 blade (not sure on current prop pitch)

          Oh, I don't particular care about whole shot as long as I can still get up on plane

          Comment


          • Bacon
            Bacon commented
            Editing a comment
            My 250's Cummins 5.9 6BTA M2 have a max of 2600 rpm. The engines have a governor so they would not rev much beyond rated, maybe +/- 50 RPM. You sure you have 250s? Or maybe they are Hino 250s?

          #6
          My 270's are rated max 2600 so 250hp wouldn't be more. I'd say post 5 is seriously under propped. Post 1 is over propped.
          1989 26' then 1994 32' now 2001 39'

          Comment


            #7
            Thanks Uncle Bob. So increasing the pitch on the props... How does that affect cruise & low speed fuel economy? Will I get a higher top end speed (over 22kts) in theory?

            Comment


              #8
              Jeff: Plan on 200 rpm for every inch of pitch change. That's a guide not deadly accurate, but close. If your average is 2850 and you should be 2600 then you are 10% under propped and the prop shop will pitch up 10%.
              If you increase pitch, you increase speed, so less fuel (lower rpm) at your usual cruising speed and higher top end speed at the rated 2600 rpm.
              1989 26' then 1994 32' now 2001 39'

              Comment


                #9
                Originally posted by jeff.osterberg View Post
                Thanks Uncle Bob. So increasing the pitch on the props... How does that affect cruise & low speed fuel economy? Will I get a higher top end speed (over 22kts) in theory?
                "How does that affect cruise & low speed fuel economy?"
                The affects of prop changes to low speed fuel use are mostly negligable with diesels as they run on a variable fuel mix not a fixed fuel/air mix like gas engines.
                Propping for the high end at rated WOT + 3-5% is best practice.
                Northport NY

                Comment


                  #10
                  And yet as a young boater, I thought: I’m never revving my cruiser/yacht/houseboat past 2krpm... so I should over-prop it so i get max speed on target fuel consumption. So prop bigger.

                  but then there is that whole ‘load on the engine at lower speed’ thing...

                  i still haven’t cracked the code.

                  I can tell you, though, that when I had a 4cyl Volvo penta pushing a non-planing 46ft houseboat, the prop shop sold me a prop and said ‘this is what you want but do not, ever, go over 3000rpm with it (even though a late 80’s Volvo 230B can max RPM around 4400rpm). So I put that prop on and loved it! I don’t think I burned 100gal in a season and I was out cruising all the time. Every weekend and more.

                  so what’s the real answer? I don’t know. I DO know that my 22x22 inboard nibral props on my dual 454 3587 are not cheap. So a re-prop would be super expensive.

                  Comment


                    #11
                    Originally posted by Jid View Post
                    And yet as a young boater, I thought: I’m never revving my cruiser/yacht/houseboat past 2krpm... so I should over-prop it so i get max speed on target fuel consumption. So prop bigger.

                    but then there is that whole ‘load on the engine at lower speed’ thing...

                    i still haven’t cracked the code.

                    I can tell you, though, that when I had a 4cyl Volvo penta pushing a non-planing 46ft houseboat, the prop shop sold me a prop and said ‘this is what you want but do not, ever, go over 3000rpm with it (even though a late 80’s Volvo 230B can max RPM around 4400rpm). So I put that prop on and loved it! I don’t think I burned 100gal in a season and I was out cruising all the time. Every weekend and more.

                    so what’s the real answer? I don’t know. I DO know that my 22x22 inboard nibral props on my dual 454 3587 are not cheap. So a re-prop would be super expensive.
                    "And yet as a young boater, I thought: I’m never revving my cruiser/yacht/houseboat past 2krpm... so I should over-prop it so i get max speed on target fuel consumption."
                    If it was a gas engined boat you could save some fuel at very low speeds by overpropping - but there is that overload thing that can cost a whole bunch.

                    Northport NY

                    Comment

                    Working...
                    X