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Jackshaft Balancing

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  • Jackshaft Balancing

    I Was Told There Was A Post ,on The Way To Balance My Jackshafts - Have A 28 With Diesels- Which Post Are These Found On -new Member-love The Boat - Thanks

  • #2

    pm "outriggers" he has a copy of it. we just got thru doing ours on sunday.


    • #3
      Jackshaft Balancing Procedure

      Use Extreme Caution For This Entire Procedure. Keep All Body Parts And Clothing Away From The Shaft While It Is Turning. Once The Weight Has Been Added, A Protective Shield Should Be Used To Protect Against The Weight Flying Off And Striking Any Part Of The Body. Do Not Attempt To Touch The Shaft Until The Igniton Switch Is Off.

      1. While The Engine Is Cranking And Also At Idle, Check To Make Sure There Is No Wobble In The Joints. Any Wobble Will Indicate That Something Did Not Get Aligned Properly On Assembly.

      2. Run The Engine Up To Approximately 2900/3000-rpm And Check For Any Vibration. The Shaft Will Appear To Become Fuzzy As It Starts To Vibrate. Critical Speed For This Tube Is Approximately 2900/3000 Rpm. The Worst Vibrations Should, But Not Always, Occure In This Range. If Vibrations Cease Before This Range, Reduce Rpm To The Worst Vibration To Begin The Procedure.

      3. While The Shaft Is Vibrating, Lightly Touch The Shaft With A Piece Of Chalk Or Soapstone. Use Caution; Do Not Allow Body Parts Or Clothing To Get Between The Shaft And Stringer. Shut The Engine Down And Note The Mark.

      4. Place The First Weight 180 Degrees From The Mark (figure 1) And Secure With A Minimum Of 2 Layers Of 1” Nylon Reinforced Strapping Tape (make Sure That At Least One Layer Goes All The Way Around The Shaft). Do Not Cover The Mark On The Shaft; This Will Be Used To Determine Proper Weight.

      5. With The First Weight Securely In Place, Run The Rpm Up Again And Mark The Shaft Again. Use A Sheild To Protect Yourself And Others In Event The Weight Flies Off. The Second Mark Should Be Made At The Same Rpm As The First. If The Mark Moves All The Way Around To The Weight, Reduce Weight And Try Again (figure 3). If The Second Mark Is In The Same Place As The First, Add Weight And Run Up To Same Rpm Again (figure 2). If The Mark Begins To Move Around The Shaft, This Indicates That The Weight Is Close To Correct And The Final Balance Procedure Can Begin (figure 4).

      6. Once The Mark Begins To Move, It Is Simply A Matter Of Trial And Error. There Is No Further Need To Mark The Shaft Once Weight Movement Has Begun. While Paying Close Attention To Engine Rpm For Vibration Range, Move The Weight Around The Shaft Approximately 1/8” At The Time And Recheck For Vibration. As You Get Closer To The Balance Point The Rpm Range Of Vibration Will Decrease And The Balance Rpm May Increase Slightly (shaft May Vibrate Over 200/100/50 Rpm Range But The Balance Rpm May Increase Closer To The Critical Speed Rpm, 2900/3000).

      7. During The Final Balancing Procedure, If The Vibration Gets Worse Or The Range Gets Wider, Reverse Direction Of Weight Movement And Move In 1/8” Increments To Fine Tune. It Is Possible To Reach A Point During The Final Stages That Any Movement Makes Vibration Worse. If This Happens Simply Add A Small Amount Of Additional Weight In The Same Spot And Check Again. If The Vibration Is Worse, Reduce The Amount Of The Original Weight And Try Again. Weights Do Not Have To Be In The Same Spot On Shaft, Only In Approximately The Same Spot Relative To Shaft Circumfrence.

      8. Once The Shaft Is Balanced There Should Be No Vibration At All In The Shaft. After Removing The Paint And Cleaning The Shaft Under Weights, Epoxy Them In Place And Paint The Shaft To Protect Against Rust.


      • #4
        That's pretty well the correct procedure. We had vibration between 2200 and about 2900 on our 25CC. When you get near the balance point the vibration spread will decrease. We had a pretty had time doing the balance and just about gave up. We moved more forward on the shaft closer to the center and played around and the out of balance point finally started to move and moved about 90 deg. When it finally reached balance moving it a very small amount resulted in a distince out of balance condition. We ended up using three drive shaft weights (curved to fit a driveshaft) that were about 1/8" in thick and a inch or so in diameter. You can bend washers in a vice and do pretty good. They are available at a drive shaft shop. Get an assortmant if you buy some.

        Out shaft never had a weight on it but I polished the shaft a little with a grinding disk to get rid of the very rusty condition. I guess this threw it out of balance.

        I have a procedure about the same as the above on in Ms Word format if you want it.
        Advance, NC


        • #5
          i had a 25 before my 28 and solved the balance problem more safely by bringing it to a drive shaft shop. don't know at what speed he balanced it, but it worked fine.


          • #6
            A drive shaft shop could use the same procedure to balance it or mount it on their balancing machine if they have one. The problem with balancing the shaft out of the boat is that there may be minute misalignment when it is reinstlled. Most shops don't have a way to mount a shaft with CV jounts on the end. They would have to make adaptors for each end which wouldn't be worth it unless they had a lot of them to do. I tried that route as a shop here has a $100k balancing setup.
            Advance, NC


            • #7
              Hey Thanks

              Hey Thanks Guys - A'm Going To Try It This Week-will Let You Know How It Goes-thanks Again


              • #8
                Balancing Complete

                Got A Hand Full Of Driveshaft Wieghts From Standard Parts For 2.50 -dad Couln't Wait For Me -he And My Good Friend John P. Went Down And Balanced Them Said It Wasn't Bad At All- J B Weilded Them In Place - Will Do A Test Run This Sat. -might Be More Vibrating Than Shafts Supposed To Blow 20-25 -thanks For The Help- Keith At Cc Has Been Outstanding To Work With Too -super Job