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Thread: Prop size question

  1. #1
    Lumpy
    Hello,
    I was checking out the underneath of the boat now that it is in the garage for the rest of the season. I found that the prop nuts were finger tight. How tight should they be? Any certain torque or what? Also, I saw on the prop it is an OJ 12x15 and it says cupped on it. Is this a prop normally used for pulling skiers or is it your standard sized 3 blade? I don't ski much any more so I am thinking this prop is killing my top end. This boat is used for cruising and hauling ass. What prop size would you recommend? I am not sure of what gears I have in my v-drive. Thanks......Lumpy

  2. #2
    FlatRat
    Lumpy,
    I'm farely new in this but they say that the OJ brass three blade should be a paper weight.I took one off BBC Sanger flat and went from 5,500 to 6,800 rpm's.What a whole shot and top end too.

  3. #3
    missilemud
    Lumpy:
    Hello,
    I was checking out the underneath of the boat now that it is in the garage for the rest of the season. I found that the prop nuts were finger tight. How tight should they be? Any certain torque or what? Also, I saw on the prop it is an OJ 12x15 and it says cupped on it. Is this a prop normally used for pulling skiers or is it your standard sized 3 blade? I don't ski much any more so I am thinking this prop is killing my top end. This boat is used for cruising and hauling ass. What prop size would you recommend? I am not sure of what gears I have in my v-drive. Thanks......Lumpy

  4. #4
    FlatRat
    Oops,
    I went from 12x16 brass three blade to a 12x15 steel two blade.Hallcraft box with 17 over gears.

  5. #5
    missilemud
    oops i mean to write something too .. ok that prop nuts should be balls tight , if there loose then good thing you found it now. i like to put a dab of silly-bone on the shaft before install,only because water gets in there.i use a lock nut on my shafts , with a little blue loc-tight

  6. #6
    126driver
    Lumpy - you need to find out what gear you have in the box. Don't bother tightening up that prop nut. Back it off all the way and pull that brass three-blade off. You're going to want a steel two-blade but you need to tell us what you're running for a motor first.

  7. #7
    Lumpy
    Thanks for the replies guys.....
    126Driver,
    I bought the boat in June of this year from a 70 year old guy who has had it since new. He said it is a 1969 427. He said when it was rebuilt they put a slightly bigger cam in it but thats about it. It has a single 850 double pumper on an edelbrock intake. I ran the numbers on the heads which is 3964291 and these are the specs....69-70 rectangle ports..closed.. 109cc chamber. I drove the living piss out of it this summer and it ran flawlessly. I was very impressed! I remember hearing how you can determine your gear ratio by counting the shaft rotations. Can someone please tell me exactly what I need to count and line up to figure out what gears I have? Thanks......Lumpy

  8. #8
    CircleJerk
    Lumpy, If that's a Casale split case, the gear ratio is stamped on the aluminum spacer-mount that the two sides bolt to. Look at the very bottom if the v-drive is out of the boat. Pulling the front case for gear inspection is a snap IF you have a top bearing puller. Super Dave sells them. It's always good to check bearings, change the oil, and check for metal fatigue or debri. Now you can remove the gears and read the stamped numbers for ratio identification. Also note if any water, rust, damage has occured. V-drives should have the oil changed every year and you may do so without pulling the cases apart by removing the very bottom bolt on the 5 or 6 bolt shift pod. it drains very slow but you have all winter right? We use Amsoil 2000 90weight gear oil in our race boats gear box and love it!
    The bronze prop is for skiing under 5000 rpm so the steel blade is a good investment for speed as well as safety. Remember it's spinning more than engine rpm unless you gear ratio is 1:00. A common ratio is l:15 {fifteen percent}, 1:18, or 1:12 etc. Consequently, you can fling a prop blade and ruin your day! This is what the experts say but I have never seen a prop failure and dont want to!... Just one Jerks opinion.... PS refer to a thread entitled 'Prop Nut' for more info on that loose nut.
    [ November 09, 2002, 01:45 AM: Message edited by: CircleJerk ]

  9. #9
    058
    Yeah... that "prop nut" thread reads like War and Peace. Everything you wanted to know, thought you knew and some things you didn't need to know are covered in that thread.

  10. #10
    126driver
    Lumpy,
    Pull the gears and check everything out. That way you'll know for sure what's going on with the box. Click on the banner above and email Tom at Menkens. He'll hook you up with a prop. Probably 11.5 x 15 or something like that.

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