Jtrew Boat Speed Question

Discussion in 'Boat Tips' started by jtrew, Dec 15, 2005.

  1. jtrew

    jtrew New Member

    Messages:
    4,404
    State:
    Little Rock, AR
    Anybody out there water ski? Technical question: How fast does the boat need to be going to pull one 175# person on a slalom ski? I've got a 20' Kenner Ski Barge with an 85hp Mercury on it that I'm trying to get fixed up, and I'm curious as to what the top speed will be on it. A friend of mine back in the late 60s had a 19' Ski Barge with a 60hp Mercury on it, and it would pull one of us on a slalom ski; it wouldn't pull two. It had no speedometer, so I don't have a clue as to how fast we were going, but if I could find out, I could use that info to estimate how fast the slightly larger Ski Barge with 1/3 more horsepower should be.
     
  2. on_the_fly

    on_the_fly New Member

    Messages:
    606
    State:
    Kentucky
    i weigh 260 lbs an i can ski behind any boat that will run atleast 20 mph but idealy 35 to 40 is perfict speep for skiing. the bad part is an under powerd boat makes it harder to get a skier going. an a beginer skier probly couldnt get out of the water just because they are expecting the boat to do all the work for them an thats not true. but if you are only useing one ski then you probly know how an one ski is easer to get up on than two for a person that knows what they are doing. my boat is 16 foot with a 90 hp johnson an it runs 40 top speed i changed the prop an i have a realy great hole shot.
     

  3. jtrew

    jtrew New Member

    Messages:
    4,404
    State:
    Little Rock, AR
    Thanks. I once had a 20' deep-V Robalo and 135hp Evinrude that would run 40mph on calm water with 2 people aboard, but that's a totally different rig. I had to run 22mph just to stay up on plane with that boat. The ski barge is more like a great big jonboat, even though it's made of fiberglass; it has a very flat bottom, and is a very light hull for its size.
     
  4. Mr.T

    Mr.T Active Member

    Messages:
    2,554
    State:
    MO
    30 to 35 mph is plenty fast for slalom skiing. You can certainly do it at 25mph or maybe even less, but it's not much fun. Anything over 35 mph and you're asking for some good bruises when you wipe out.

    Doesn't take a lot of horsepower to go that fast. But it takes a lot to get you out of the water on one ski. If you're going to start out on two and drop a ski, HP doesn't matter nearly as much.

    All I know for sure is my 200 Merc Optimax will pull your arms out of the socket... :eek:
     
  5. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Jerry I'm no expert but I'm gonna guess you should be able to exceed 35 with the Kenner.Mercury has a propeller website where you can enter the type of boat,weight or lenght,size engine and it will give you an approximate speed with different props.Haven't used it myself in a while so I may be forgetting something.Your rig would certainly pull one skier for sure size immaterial (Up to a point) possibly two_One thing for sure it will make a good fishing boat. :0a26:
     
  6. bearcat

    bearcat Member

    Messages:
    925
    State:
    Nokomis, Illinois
    Hey Jtrew. I use to ski all the time. When on a slalom ski it takes around 25 mph to keep the skier above water . I generally ski at 28 to 30 mph. Depends on how calm the water is. by the way I weight 180. So that should give you an idea for you question.
     
  7. jtrew

    jtrew New Member

    Messages:
    4,404
    State:
    Little Rock, AR
    Thanks for the info. I'll be sure to check the Mercury prop website when I get everything rigged up. I've got a choice of 4 different props: 2 SS; 1 aluminum; 1 brass. One of them came from an 80hp Mercury, and I got the other 3 with the 85 when I bought it.
     
  8. jtrew

    jtrew New Member

    Messages:
    4,404
    State:
    Little Rock, AR
    Thanks for the info. I'll be sure to check the Mercury prop website when I get everything rigged up. I've got a choice of 4 different props: 2 SS; 1 aluminum; 1 brass. One of them came from an 80hp Mercury, and I got the other 3 with the 85 when I bought it. Anybody needs 80hp Mecury parts, let me know.
     
  9. MoMudCat

    MoMudCat New Member

    Messages:
    186
    State:
    Troy,MO
    28 to 30 mph is a very comfortable speed to slalom for me. It's been a few years since I've skied, but that used to be all I did in the summer. If you are running a course I think you will need more around 35+ mph. I've skied behind a lot of different boats. Some I could dang near stop when I cut, some would almost jerk me out of the water. Neither were as fun to ski behind as a good heavy boat that would pull a steady 30 mph! Other things to consider are weight distrubution and driver skill.
     
  10. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Jerry you will need the size and pitch of the props to work the database for a speed estimate.I think the most accurate way to get a speed picture is to have a very good estimate of the total weight of the boat with everything you will have in it when you run it.That would include fuel fishing gear etc etc and dont forget the engine weight.
     
  11. jtrew

    jtrew New Member

    Messages:
    4,404
    State:
    Little Rock, AR
    I haven't looked on the Mercury props, but I assume that the info will be stamped on the prop like it is on my Yamaha prop.
     
  12. jim

    jim New Member

    Messages:
    2,579
    State:
    Jacksonville NC
    Yes same place.You might have to clean the hub a little bit to see it.
     
  13. zappaf19

    zappaf19 New Member

    Messages:
    1,574
    State:
    Monticello,IN
    I use to ski my summers away. My favorite speed for one ski was 33. Not alot of drag on the ski @ that speed which means not alot of pull on your arms. We had a 85 hp johnson back in the old days.
    Bill