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85hp Upgrade Carb & Prop Question

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  • 85hp Upgrade Carb & Prop Question

    Well my engine is giving me fits, so while I am at it, I am thinking it might be time to pursue the c85 upgrade. I am fortunate in that the STC was already purchased by a previous owner, just never installed. I am looking at an 85-8 on a short mount to keep it certified non-electrical and weight down.. As I will need a carb, is it worth upgrading to the Marvel vs tracking down a Stromberg? (I have a strombuerg on my a65 currently.) Also is it worth installing a mixture control?

    Lastly any climb prop recommendations as my 7442 isn't going to cut it. I am just trying to get an idea of what to look for to start and then can dial it in.

    I have tried to read through all the old archives on here regarding the upgrade but still have a few holes I am trying to fill in. Thanks in advance.
    Stu

    '46 BC12D
    Jefferson County (0S9)

  • #2
    I don't know if the 85 marvel had accelerator pump in it. I also don't know what altitude you operate at. You can modify your stromberg to 85 config with venturi and jet swap.

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    • #3
      My MA-3SPA has a pump. https://msacarbs.com/product-categor...ty=c-85-series

      Gary
      Attached Files
      Last edited by PA1195; 05-14-2019, 19:50.
      N36007 1941 BF12-65 STC'd as BC12D-4-85

      Comment


      • #4
        I don't think the Marvel would be worth the extra $$. Yes, hook up the mixture on the Stromberg and enjoy! They're great carbs, just don't act exactly like most people expect them to. What's wrong with that prop? Is it the full 74"? I'd measure and make sure. Mine's running a 74-2x42 and I liked it. There was a good thread on here not long ago that had some great observations by a couple of guys on props.
        John
        I'm so far behind, I think I'm ahead

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        • #5
          Flying in real cold the Marvel works better due to the pump. I never flight high enough to use a mixture control.

          Gary
          N36007 1941 BF12-65 STC'd as BC12D-4-85

          Comment


          • #6
            I run the Marvel and I think that the longest prop you can legally run is 74" if you use the type cert. data sheet from the Aeronca on floats with an 85, I posted the information on it a few years ago. I would just install a derated o-200 and run a McCauley 7443, Oh wait, I am! hahaha
            N29787
            '41 BC12-65

            Comment


            • #7
              Thanks for the info. Seems like the Marvels are preferred but come at a higher price tag. The airport I am out of is sea level but I can be up to 7,000 in the mountains pretty easy.

              Everything I have read for the Taylorcraft c85 TC limits to a 71" for a McCauley and 72": for the sensenich. My 7442 is a full 74". Can you make RPM with a 74" on an 85?
              Stu

              '46 BC12D
              Jefferson County (0S9)

              Comment


              • #8
                I'd ask here about a C-85 or O-200 installation and prop - https://dc65stc.blogspot.com/2018/12...explained.html

                A C-85 will turn a prop up to 75" with the right pitch (38) to rated static but may not be approved. I run an approved Sen 74-40 on a C-85 but it's a 200ci stroked engine and approvals are often a thing of history. Again ask Terry Bowden for his guidance.

                Gary
                N36007 1941 BF12-65 STC'd as BC12D-4-85

                Comment


                • #9
                  Thanks. I spoke with Terry (He's been really helpful with the process) and he recommended a M72CK-2-44 for a climb prop. I was just curious what others were using/having results with. Honestly I was a little surprised to see the c85 limited to a 71/72" prop length but being able to run the 74" on the a65.
                  Stu

                  '46 BC12D
                  Jefferson County (0S9)

                  Comment


                  • #10
                    Originally posted by Kerbs View Post
                    Thanks. I spoke with Terry (He's been really helpful with the process) and he recommended a M72CK-2-44 for a climb prop. I was just curious what others were using/having results with. Honestly I was a little surprised to see the c85 limited to a 71/72" prop length but being able to run the 74" on the a65.
                    You probably meant Sen M74CK-2-?? Read the TCDS 1P2 for Sensenich props below and note the approval of a 74CK-2 for a C-85 as well as 76AK-2. I run the latter as it was approved by Sensenich for both a C-85 or C-90 which the C-85 Stroker in my case is configured as. Taylorcraft may not have approved some propellers so other approval is required. They did approve the M74CK-2 for C-85's because someone other than the aircraft manufacturer had approved it (I assume Sensenich).

                    I's also pitch the prop to yield 2350 per the static rpm max on TCDS A-696 if takeoff and climb are a priority. Pitch change is usually 30-50 rpm per inch of pitch.
                    Attached Files
                    Last edited by PA1195; 05-14-2019, 23:25.
                    N36007 1941 BF12-65 STC'd as BC12D-4-85

                    Comment


                    • #11
                      Originally posted by Kerbs View Post
                      Thanks. I spoke with Terry (He's been really helpful with the process) and he recommended a M72CK-2-44 for a climb prop. I was just curious what others were using/having results with. Honestly I was a little surprised to see the c85 limited to a 71/72" prop length but being able to run the 74" on the a65.
                      That was based on what was certified on the C-150 with the o-200, none of the other manufacturers wanted to spend the money to certify a longer prop, but Aeronca did...and if the 74 on a 65 is acceptable for the airframe, it is good for the o-200/85
                      N29787
                      '41 BC12-65

                      Comment


                      • #12
                        Here's McCauley's TCDS P-842 for their props. Note the C-85 is limited to 71" with theirs but the O-200 can go to 75".. Length does matter.
                        Attached Files
                        N36007 1941 BF12-65 STC'd as BC12D-4-85

                        Comment


                        • #13
                          PA1195, what kind of cruise are you getting with the 76AK2?

                          So from what I gather, I can run up to a 71" with a McCauley, or up to 72 or 74 with a sensenich depending on prop, based on the TC from Sensenich rather than Tcraft? I assume most people with 85's are running something in the 71" range?
                          Stu

                          '46 BC12D
                          Jefferson County (0S9)

                          Comment


                          • #14
                            Originally posted by Kerbs View Post
                            PA1195, what kind of cruise are you getting with the 76AK2?

                            So from what I gather, I can run up to a 71" with a McCauley, or up to 72 or 74 with a sensenich depending on prop, based on the TC from Sensenich rather than Tcraft? I assume most people with 85's are running something in the 71" range?
                            I cruise in the lower 90's at 2350-2400 (Proptach accurate) on wheels, skis, and floats at 74-40" pitch. Going to 74-42" (what the previous owner had for prop) wouldn't detract from climb much and would cruise slightly better. My static rpm can exceed 2350 at 40".

                            Now to run a 74" requires prop tip clearance from the ground so larger tires may be required like Desser smooth 8:50's or 26" Airstreaks like I have.

                            I'd ask Terry if he's willing to support one of these propellers with a C-85, C-85 Stroker, or O-200 then consider the cost and effort involved in that upgrade.

                            Gary
                            N36007 1941 BF12-65 STC'd as BC12D-4-85

                            Comment


                            • #15
                              Call me or PM. I did the C-85 [-12F] 0-200 with M-S Carb and Metal Sensi prop [74x44 or 72x44, if I recall] , Slicks, dual straight pipes and 8.50's.
                              Terry helped me out with all the details....is now a poor's man super cub STOL with 100+ MPH cruise @ 5 gal/hr leaned... you will not regret it. Max RPM is redlined at 2,550 which needs to be controlled, otherwise you will over rev the engine and actually, you dont need all that power on TO nor cruise...just to get out of a tight spot or short field or TO w/ obstructions at the end... for a short time..30 sec.

                              my 2 cents

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