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C stock Runabout help

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  • C stock Runabout help

    Hi, I have a Sorensen c stock runabout that I need a bit of help setting up. The boat has a 32" wide bottom and a side fin. The boat will porpoise at anything less than full speed. On narrow courses and in rough water this is no good. I am thinking about making the bottom narrower (22-24"). Any suggestions?

  • #2
    Have you checked the bottom to make sure it is flat? It needs to be very flat on the last 36" of the bottom.
    Sean Byrne



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    • #3
      Originally posted by n5robert View Post
      Hi, I have a Sorensen c stock runabout that I need a bit of help setting up. The boat has a 32" wide bottom and a side fin. The boat will porpoise at anything less than full speed. On narrow courses and in rough water this is no good. I am thinking about making the bottom narrower (22-24"). Any suggestions?
      Hopefully some of the C runabout drivers will pipe up.
      You might post some info on how you are setting up the boat to run. what depth under the bottom, are you running tucked, kicked out, parrallel?
      With my A runabout running with the prop shaft dead parrallel to the bottom with my best prop it also porpoises. but a 1/16" tuck and it gos away a lot sooner. Almost all runabouts will porpoise untill you reach a reasonable speed.
      The prop you are running also makes a big difference on how the boat runs and handles.
      I would NOT make the bottom narrower!!
      Gene Schertz 26V
      TEAM CAFFEINE
      Cranked up and ready to Roll
      Reeds for Speed!

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      • #4
        I know some of the Sorenson boats have a rocker built into them. If this is the case it will porpise just like you described. Some folks like that rocker,
        I personally do not.

        Flat IMO is the best. Breaking at about 36"-42" should get things where you want them. Try your set up at parrallel first after you change the bottom. Then you can tuck or kick out depending on the boats characteristics. My guess is you'll probably run about 1/8" tucked.

        If all else fails call Darrell.

        Tim
        Tim Weber

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        • #5
          Thanks to all. The bottom is perfectly flat. The boat had a rocker in the bottom, but I re-poured the bottom to take it out. The last race I ran, the motor was kicked in about 1/8". Depth is 1 3/8". I wound up in the water in the middle of the 2nd heat. I guess I skuffed off just about enough speed to put it into the porpoising region, hit a wake and it stood straight up. Also the porpoising during milling makes it even tougher to time the start right because you need to go so fast to control the bouncing.

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          • #6
            1 3/8 is way 2 deep 4 c stock u need 2 jack up ur motor 2 3/4 or just a lil bit under an ul get more speed wich will take away the porposing

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            • #7
              My D Sorenson will porpise while I'm at milling speed. Once I'm on the throttle, it's smooth as can be. All I've done to it was rub a stink block on the bottom to flatten it out a bit.
              I'm far from an expert on this stuff. I would never question Darrell's reason for makin' it the way it is. If it has a rocker built into it, he put it there for a reason. But that's just my opinion.


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              • #8
                The minimum prop depth is 3/4" below the bottom as meassured from the center of the prop shaft. Raising the motor will increase your speed and allow the boat the clean quicker.

                Sorenson boats are dynamic. You can't just sit in it. You have to " work " the boat constantly to keep it at trim. If you don't know what I mean, ask someone to give you a live demonstration. Try and find someone with runabout experience to teach you. It takes a long time to develop the feel required to work the boat properly. This is one of the reasons that hydros are so popular, you find the bubble and go.

                There are a number of really good runabout drivers out there. Next time you go to a race, quiz the guys running in the top three. You'll learn a lot.

                Tim
                Tim Weber

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                • #9
                  Practice makes perfect...

                  Laps, laps, laps... The only way to learn how to race a runabout. A properly designed runabout will want to run kicked in an 1/8" or so, if you have to kick it out to ride free then the design is flawed (by design). 3/4" below the bottom, and don't narrow it! "Loose is fast and on the edge of out of contol", (Harry Hog). Keep your bottom straight and get down and back, the rest is just a feel for the rhythm. GL
                  Last edited by Gunjumper; 11-16-2009, 06:07 PM.
                  Future J dad!

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                  • #10
                    Thanks much to all! I was following Darrell's advice to the letter with the bottom. I will try setting the propshaft C/L @ 3/4". It appears I have been running it way too deep. If I can just get it to run clean about 5mph slower, it would be a great boat.

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                    • #11
                      Originally posted by n5robert View Post
                      Thanks much to all! I was following Darrell's advice to the letter with the bottom. I will try setting the propshaft C/L @ 3/4". It appears I have been running it way too deep. If I can just get it to run clean about 5mph slower, it would be a great boat.
                      I would think that running deep would cause the prop to have more leverage against the nose. That way the tendency to porpoise might be increased so just getting to height might be some of it, run practice the rest.
                      Team Tower

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                      • #12
                        Engine height

                        Originally posted by johnsonm50 View Post
                        I would think that running deep would cause the prop to have more leverage against the nose. That way the tendency to porpoise might be increased so just getting to height might be some of it, run practice the rest.
                        That's right usually the deeper the engine (to a point) with prop shaft level with bottom the greater is the nose lift because the prop thrust force is below the center of gravity of the total rig and with the longer moment arm provides the backwards rotational torque. Tuck in reduces this and tuck out increases it. Testing is the only way.
                        Last edited by ZUL8TR; 11-19-2009, 05:40 AM. Reason: add'l notes
                        "Keep Move'n" life is catching up!
                        No man's life, liberty or property are safe while the legislature is in session.

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                        • #13
                          Agreed

                          Originally posted by Gunjumper View Post
                          Laps, laps, laps... The only way to learn how to race a runabout. A properly designed runabout will want to run kicked in an 1/8" or so, if you have to kick it out to ride free then the design is flawed (by design). 3/4" below the bottom, and don't narrow it! "Loose is fast and on the edge of out of contol", (Harry Hog). Keep your bottom straight and get down and back, the rest is just a feel for the rhythm. GL
                          CSR is probably one of the more challenging classes in stock outboard. It took me years of running lots of laps to feel comfertable. The more you're in the boat the more you will feel ready to take on gunjumper! LOL. All the advice above is good stuff, so try it out and see how it goes. My only advice is where your body is positioned in the boat. Like someone mentioned above, you can't just sit in the boat and go for the ride like a hydro. You have to work your body all around the cockpit to find the "sweet spot" or where the boat rides the best. I can tell you that CSR for me is a workout and probably the most exhausting class I drive, but it's always a blast! Constant movement to find that spot is key. Good luck to ya!
                          Kyle Bahl
                          20-R

                          "He didn't bump you, he didn't nudge you, he rubbed you, and rubbin' son is racin'!"

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                          • #14
                            Thanks Kyle, I think all of this is excellant advise. I think another thing I may need to do before next season is cut back the winshield a bit as it limits how far forward I can move. This boat really likes to point its nose up when hitting chop. I have been driving the c runabout class for about 10 years, but this boat is much more demanding to drive than the DeSilva I had been using previously,especially in rough water, but it is faster.

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                            • #15
                              Robert set the boat up with a 1/4 kick under to start with. Make sure you are up to height (3/4 below bottom). Take the boat for a ride. This should calm the lift issue's you are having. From there start kicking it out at 1/16 intervals. Always staying at the 3/4 below the bottom. Everytime you kick it out a 1/16 you will need to raise it up a 1/16. Check it when you make changes so your on the money height wise. Keep track of your GPS readings. If you are not going any faster as you kick out then being under is where you stay. When you get on the coarse with a bunch of boats the ride will loosen up and be manageable. Boat ride is everything. You don't want it popping as this is just slowing you down everytime it does it. Give it a try and i am sure you will find this is the answer to your problems. If you have any other questions give me a call 1-248-568-4622 Mikey
                              Last edited by mike ross; 11-19-2009, 10:04 AM.
                              mike ross

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