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38xx - Prop / tunnel clearance...?

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    38xx - Prop / tunnel clearance...?

    PO had advised me he put biggest props that would fit when he repowered with the cummins 210's...21x26x4...

    I do get WOT under load but it looks like turbulence is damaging the trailing edge of the tunnels...

    Are you 38'ers running 21's...? And if yes are you seeing anything like what I've described...?

    Thanks in advance...Nick
    1988 3888 "Liberty"
    Twin Cummins 6BT's 210hp
    Onan 8.0
    Boating Raritan Bay

    #2
    20x20 is what I have with my old 175’s. That means you are only coming a half inch closer from the tip of the blade to the tunnel. 26 is a pretty big bite, I’m surprised that you can run that much more prop, although I don’t know what the later model 38’s had with the larger engines. I might take a walk around Dagmars a do a bit of a survey of prop sizes.
    How about some pictures of your damage?
    P/C Pete
    Edmonds Yacht Club (Commodore 1993)
    1988 3818 "GLAUBEN”
    Hino EH700 175 Onan MDKD Genset
    1980 Encounter Sunbridge "Misty Blue" (Sold)
    MMSI 367770440
    1972 Chevrolet Nova Frame off Resto-mod in the garage
    Boating on the Salish Sea since 1948

    Comment


      #3
      Boat's in the water so pics not for a while...

      It's definitely turbulence damage...

      Yeah...I was surprised by the 26...will verify when the boat goes on the hard but that's what is on the repower paperwork...

      Assuming most are sporting 20's, I'm likely to cut mine down a bit. Don't want the damage to get worse.

      Thanks for the survey offer...

      1988 3888 "Liberty"
      Twin Cummins 6BT's 210hp
      Onan 8.0
      Boating Raritan Bay

      Comment


        #4
        I'm running 20 x 21.

        David

        Comment


        • Nickp
          Nickp commented
          Editing a comment
          Thanks, David...thinking won't find anythi,g bigger than 20...

        #5
        Nick, I learned that finding prop sizes can be a challenge. Of those I did find, I have no knowledge of what power each boat has. 2- 20x22; 3- 20x20; 1- 17x17. I did a drive by of quite a few more and didn’t see anything that appeared to be larger than 20”.
        P/C Pete
        Edmonds Yacht Club (Commodore 1993)
        1988 3818 "GLAUBEN”
        Hino EH700 175 Onan MDKD Genset
        1980 Encounter Sunbridge "Misty Blue" (Sold)
        MMSI 367770440
        1972 Chevrolet Nova Frame off Resto-mod in the garage
        Boating on the Salish Sea since 1948

        Comment


          #6
          I don't think damage to the tunnels is that uncommon, here is a pic of mine after I had the bottom soda blasted last year
          1989 3888
          Hino 210's

          Comment


          • Nickp
            Nickp commented
            Editing a comment
            Thank you...mine is a bit deeper and about an inch long...what diameter props...?

          #7
          Thank you, Pete...not surprised at finding 20's...when I saw the small amount of clearance and the damage I figured I'd be getting them babies cut...

          The aren't hitting, good thing. Just don't know why it didn't show up in the survey...or how I missed it. Oh, well...

          Thanks again...
          1988 3888 "Liberty"
          Twin Cummins 6BT's 210hp
          Onan 8.0
          Boating Raritan Bay

          Comment


            #8
            There are all sorts of sizes and blades out there. How’s the time to start working with a go-to prop shop. IIWM, I’d ask around, visit a few shops then have a serious talk about going about getting the boat propped correctly. That may be by reconfiguring your current props. If you are a member of a yacht or boating club, use that network. If you are not a member of a club, give it some serious thought.
            P/C Pete
            Edmonds Yacht Club (Commodore 1993)
            1988 3818 "GLAUBEN”
            Hino EH700 175 Onan MDKD Genset
            1980 Encounter Sunbridge "Misty Blue" (Sold)
            MMSI 367770440
            1972 Chevrolet Nova Frame off Resto-mod in the garage
            Boating on the Salish Sea since 1948

            Comment


              #9
              Thanks, Pete...great minds think alike.

              I've been working with the shop that did the repower to the 210's (2012). The boat cruises nicely and achieves WOT...good fuel consumption...gets to WOT speed at 2600 - 2650 (all measurements at slack current). Although I have not yet strobed the engines for accuracy of the tachs... From the survey "Wide Open Throttle testing achieved 20.1 knots @ approx. 2600-2700 rpm." "Cruise testing achieved 17 knots @ approx. 2300 rpm."

              The only issue I have with the configuration is that the prop diameter does not seem to allow sufficient clearance to the tunnel. Working with the original shop yielded the same...cut the prop to 20" is the only thing that's left. The shop that did the original work just did not anticipate the water turbulence would chew away at the tunnel edge. Their initial impression was that I caught a tree branch or something...WHAT...?!?!?

              I took it out for a ride last night and, as expected for this time of year in the Northeast, I've developed some bottom, prop and tabs muck...so I'll be pulling it in the next week or so to clean it up...I will be able to see if more of the tunnel edge has been chewed. Yes...I'll get some pics...

              I have also discussed this with others but few give as much technical consideration and would rather "just change the props"... I can't imagine getting better results...

              I do currently belong to a club and have been in one other since early 80's...only one other 38 with the original Hino's and he's running 20"...no signs of wear on the tunnels. Others running around in Vikings, Trojans, Tiaras, SeaRays and Bertroms think I should not have bought the 38 because of little rise in the transom (see how conversations can run astray...LOL...) I offer them another beer and conversation quickly changes...

              I'm still interested in hearing if anybody else out there is running 21's in their tunnels...




              1988 3888 "Liberty"
              Twin Cummins 6BT's 210hp
              Onan 8.0
              Boating Raritan Bay

              Comment


                #10
                Here’s some data to help with the deadrise controversy. https://www.boatingmag.com/all-aboar...eadrise#page-3 Most owners don’t really understand the implications of hull shape unless they are Naval Architects. It’s not just a single number, but a system. I have yet to see a keel hanging off a Bertram or Viking, which, IMO, are great brands. It’s a matter of which comprises meet your goals and comfort. Btw, while I’m not sure about your Cummins, I’ll gladly compare fuel bills on a head to head trip.
                P/C Pete
                Edmonds Yacht Club (Commodore 1993)
                1988 3818 "GLAUBEN”
                Hino EH700 175 Onan MDKD Genset
                1980 Encounter Sunbridge "Misty Blue" (Sold)
                MMSI 367770440
                1972 Chevrolet Nova Frame off Resto-mod in the garage
                Boating on the Salish Sea since 1948

                Comment


                  #11
                  I have twin 4-bladed bronze “Nibro” propellers [Port 20 x 22 LH and 20 x 22 RH Starboard] according to my survey. Not sure if that is good or bad.
                  P/C Bob Hicks JN
                  Dock Holiday, 1992 Bayliner 3888 Double Cabin Flybridge Cruiser
                  Twin Hino W04TI 210 HP Diesels with Hurth HSW630A 2.0:1 Trannys
                  Westerbeke 8.0 BTD-614 8KW Genset
                  Avon 9 ft 6 in Tender with a Tohatsu M8B 8HP outboard
                  Currently moored at Stones in Nanamio, B.C.

                  Comment


                  • Nickp
                    Nickp commented
                    Editing a comment
                    Thanks, Bob...

                  #12
                  My understanding is there are engineering rule/formula around the minimum clearance between the edge of a prop and the hull. If I remember correctly the prop diameter also fits into the formula. A GOOD prop shop should be able to tell you the minimum distance for your particular prop and hull.
                  16' lap straight with B&S inboard, my 1st commercial fishing adventure
                  17' run about with original 80ph Volvo, fun with some exploration of the coast
                  25' Chris Craft - lots of fun exploring further north on the BC coast
                  32' wood commercial salmon troller - ice boat, hard work & fun
                  41' wood commercial salmon troller - ice boat, hard work & fun
                  38' Permaglass commercial salmon troller - freezer boat, harder work & fun
                  1987 3870 with 175 Hinos - back to mostly fun again & exploration

                  Comment


                    #13
                    From the Michigan Wheel propeller site:
                    What is the minimum allowed clearance between the propeller blade tips and hull bottom? How much space should exist between the propeller and strut or keel?

                    The clearance between the propeller blade tips and the hull bottom should be at least 15% of the propeller diameter and ideally, 20% or more. So for example, a 20” diameter propeller would have 3” minimum clearance and better still 4” or more. A common guideline for recommended propeller to strut or keel clearance is 20% of propeller diameter measured between the propeller blade edge and strut leg or keel. This is often measured at a point on the propeller blade edge about 70% of the distance from the shaft centerline to the blade tip.

                    Jim Gandee
                    1989 3888
                    Hino 175's
                    Fire Escape
                    Fyrflyer@ca.rr.com

                    Comment


                      #14
                      I am still struggling with how a prop that far out of square would be close to right compared to other people who have similar hp and operating RPM. One inch of diameter and 5in of pitch is huge for only 35hp.

                      only thing I can think is transmission on the Cummins is not the 2:1 that were used on the hino
                      1989 3888
                      Nobody gets out alive.

                      Comment


                        #15
                        Cummins produces about 525 ft lbs of torque at 2000 rpm, the Hino 175 305 at 1800. That’s a lot more torque to push the props around.
                        P/C Pete
                        Edmonds Yacht Club (Commodore 1993)
                        1988 3818 "GLAUBEN”
                        Hino EH700 175 Onan MDKD Genset
                        1980 Encounter Sunbridge "Misty Blue" (Sold)
                        MMSI 367770440
                        1972 Chevrolet Nova Frame off Resto-mod in the garage
                        Boating on the Salish Sea since 1948

                        Comment

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