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Thread: Leopard 4074 1650 KV

  1. #1

    Default Leopard 4074 1650 KV

    Running this motor on 4s and it seems to take a few seconds to get up to speed. Running 645 prop 30" deep V. Is it because of the low KV on 4s batteries are SMC 7200 90c. Boat seems very slow to come on plane, runs decent when on plane just slow to get there.

  2. #2

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    I'm not sure what motor you were running before. Could be the new motor is a little heavier than your last motor. have you tried adjusting the strut / prop angle to see if that helps at all? I had problems with my hydro coming on plane after i did a motor change. I adjusted the strut so the prop was a hair deeper in the water and problem solved.

  3. #3

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    thats a 6s motor .if you wanted to run 4s you should have got a higher kv motor .i am contemplating a motor change for my bj29 v3 .my research has told me lower kv for 6s and higher kv for 4s .

    i am still new to boats myself so someone with alot more knowledge should come along .

  4. #4

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    No motor prior. Have played with the strut not much difference boat just seems slow out of the hole.Almost seems like the motor is bogging down.

  5. #5

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    Big thing to remember you typically want the motor running between 25-30000 rpm for messing around. 35-40000 or higher for saw runs. Kv rating x voltage gives you unloaded rpm. 1650kv x 14.8v = 24420 rpm.
    1650kv x 22.2 = 36630 rpm.

    Higher rpm generally = faster

    There are lots of things to take into account for boats though.

    Hope that helps.

  6. #6

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    Had the motor prior kind of knew it was A 6s motor based on kv. Was kind of surprised at how it seemed sluggish on 4s. I knew it wouldn't have good top speed but I thought it would have performed faster out of the hole.

  7. #7

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    is it new ?

  8. #8

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    Bought it off another forum member, stated it was only used once or twice. Motor at speed sounds fine. Probably just going to run the boat on 6s. Just looking for more of a fun cruiser at around 35-40mph. Thought I could do it on the 4s. Boat ran 33mph but it was windy and choppy conditions and didn't like the out of the hole performance. Probably will just run a smaller prop for 6s.

  9. #9

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    Quote Originally Posted by Newboater View Post
    Probably will just run a smaller prop for 6s.
    a 447/3 outta do it...
    Zelos 36 Twin, Voracity 36, Impulse 31 V3, Mini Zonda 27, Delta Force 26, Offshore Infinity, Vac-U-Tug Jr

  10. #10

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    not my cup of tea putting 447/3 props on a 30 inch mono
    6s and a 42mm prop with that motor would be a better idea i guess

  11. #11

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    looks like with that kv motor you will need to go 6s plus don,t go too big on the prop size, start small and work up. my pick for the mono is a 440 x 3 for starters or maybe thats the one. oh. what size esc are you running ?

  12. #12

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    Quote Originally Posted by iop65 View Post
    not my cup of tea putting 447/3 props on a 30 inch mono
    Clearly a failed attempt at humor.
    Zelos 36 Twin, Voracity 36, Impulse 31 V3, Mini Zonda 27, Delta Force 26, Offshore Infinity, Vac-U-Tug Jr

  13. #13

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    You are running this in the "Princess" yacht correct? Based on your video I think it moves pretty good, not sure how much more speed that hull can deal with before getting out of control.

    https://forums.offshoreelectrics.com...cht&highlight=
    NEVER SATISFIED RACING
    Fine Design 32 V-Hull 4082+6s

  14. #14

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    Quote Originally Posted by Tamelesstgr View Post
    You are running this in the "Princess" yacht correct? Based on your video I think it moves pretty good, not sure how much more speed that hull can deal with before getting out of control.

    https://forums.offshoreelectrics.com...cht&highlight=
    That is correct here is the video
    https://youtu.be/bFRzG-ug914

    In the video it was 15 plus mph winds and the water jacket was leaking and filling the hull. I fixed the water leak as the water jacket was to far forward. In that video speed was 32mph on 645 prop. Went out the next day and boat ran completely dry but the wind almost blew it across the lake. I use the speed calculator on the forum and for me it is consistently off by about 8mph always faster then what I get, so I am starting to wonder if I am setting things up wrong.

    The boat is running a Raider 150 amp esc. Just wondering if 40mph is attainable on 4s and 1650kv. I see some people run 5s how does that work if one pack is heavier then the other? and the packs are on the left and right sides of the hull and don't weigh the same.

  15. #15

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    Okay just found a video of a pursuit with same set up 4074 1650 kv on 4s ran 35 and 6s ran 45 so I am not that far off being the pursuit is a lot lighter and not as deep a V.

  16. #16
    Join Date
    Aug 2010
    Location
    uk
    Posts
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    Default

    Boat is running with the bow to low = wet running, on that chop it should be flying faster than 32mph. Where is the cg on the boat, needs to be around 30% from the transom not including the overhang at the rear. Also check stinger angle that its not pointing down prop end ( negative angle ).

  17. #17

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    Quote Originally Posted by martin View Post
    Boat is running with the bow to low = wet running, on that chop it should be flying faster than 32mph. Where is the cg on the boat, needs to be around 30% from the transom not including the overhang at the rear. Also check stinger angle that its not pointing down prop end ( negative angle ).
    Boat is close to 30% cog stinger is level with the bottom of the boat. What do you think the speed should be.

  18. #18
    Join Date
    Aug 2010
    Location
    uk
    Posts
    2,617

    Default

    I would at least expect to see the boat bouncing off off some of that chop but its running pretty flat.

  19. #19

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    How about trying a 447.
    You will likely see speeds less that what the speed calc gives you due to the size and bulk of the boat. While you are probably using a 25% slip in the calc, the superstructure of your boat will make a fair bit of extra wind resistance over a race hull, this will cause the boat to run slower than you think it should, in effect greater prop slippage. Plus wind and chop will play their part.
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

  20. #20

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    I was thinking the 645 might be an issue as well.
    NEVER SATISFIED RACING
    Fine Design 32 V-Hull 4082+6s

  21. #21

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    Prather 225 or 230 may work. I have had good success on my Q mono with them, they run better than octuras on that boat.
    NZMPBA 2013, 2016 Open Electric Champion. NZMPBA 2016 P Offshore Champion.
    2016 SUHA Q Sport Hydro Hi Points Champion.
    BOPMPBC Open Mono, Open Electric Champion.

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