Installing propellor shaft into steel boat

Discussion in 'Boat Design' started by parkland, Feb 3, 2013.

  1. parkland
    Joined: Jul 2012
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    parkland Senior Member

    Lets pretend we have a 30 ft or whatever steel trawler.

    Engine is sitting where it's going to be bolted in, transmission is bolted on, and now it's time to cut a hole in the bottom of the boat, and install the propellor tube, and shaft.

    I'm assuming what someone would want, is this:
    http://www.ebay.com/itm/MASTERCRAFT..._Accessories_Gear&hash=item563b522587&vxp=mtr

    Or a variation of that to suit the needs.
    I keep searching and end up with toy racing boat results :(


    I'm looking for instructions of how everything is supposed to be constructed from the transmission to the propellor.

    Silly, a simply shaft, and I can't find much on it.
     
  2. parkland
    Joined: Jul 2012
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    parkland Senior Member

    Is it just as simple as welding a tube into the hull, installing the propellor driveshaft with marine bearings, installing a packing box, and thats it?
     
  3. tunnels

    tunnels Previous Member

    lots to think about here !!!

    The unsupported length of the shaft from the rear bearing to the packing stuffing box and bearing at the front end of the tube and shaft and coupling . always remember the shaft is taking oll the torq of the motor to nurn the shft an when it getts to the back the propellor is trying to screw its way forward and is pushing the boat so the shaft is doing lots a work not just turning but pushing and when you want to go backwards its trying to pull out the back and drag the motor and gear box with it An unsupprted shaft can be a dangerous shaft. so there some thinking to take place here !! . In glass boats we used glass tube and when all the fittings were in place a hold was drilled in the tube and then hot tallow was poured in and completely filled the tube till it gribbled out and eventually went back to being semi solid again . In 5 years of service on charter launchs not one single thing ever went wrong no leaks no noise no movment shafts were drawn out each 6 months to inspect for twist etc ,Nothing !!!. the dia of the shaft used is critical depending on the type of service and type of work and the horse power thats on the driving end !!
    I have seen shafts in Tahiti fishing boats that has almost a 1/4 of a turn of twist in a shaft because the shaft was long and had a big 3208 turbo'ed cat diesel driving back to a big 4 blade prop . They use to have a habit of chasing fish miles off shore and then going straight into reverse to stop when they got close to the fish and the shaft would wind the end of the shatf off at the gear box coupling and shaft and prop would get sucked out the back and dissapear into very deep water . There was always a tappered wooden plug and a hammer on a rope lashed to the stuffing box to fill the hole and stop the boat from sinking !! :eek:
     
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  4. parkland
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    parkland Senior Member

    The actual driveshaft I'm not to worried about, just a hardened rod that can sit in pillow block bearings.

    I am interested in the tube that gets welded through the hull, and the shaft and parts that need to be installed.

    Is there anywhere you can buy a kit for this?
     
  5. rasorinc
    Joined: Nov 2007
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    rasorinc Senior Member

    The Glen-L site and forum has a lot of info on installing in-board drive shafts and stuffing boxes. http://www.glen-l.com/ It is shown on wood boats but should be the same on steel except for welding.
     
  6. michael pierzga
    Joined: Dec 2008
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    michael pierzga Senior Member

    Sure...do some googling...steel propellor shaft tube assembly... stern tube ...shaft seal or similar . Many suppliers.


    Here...try this Vetus site...use Vetus.nl in Europe for info, not vetus US. Vetus US site is wonky. Look at the catalogue then go to the Manuel's section for parts breakdown and installation ..
     
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  7. gonzo
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    gonzo Senior Member

    It is really simple. You weld a tube that is fairly aligned with where the shaft will be. Install the shaft and align it. Then slide the cutlass bearing and weld it in place using the shaft to hold it aligned. The inside end of the pipe gets a stuffing box. That is all that it takes. I have build many boats and find that they make it sound like it is some kind of arcane secret science.
     
  8. tom kane
    Joined: Nov 2003
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    tom kane Senior Member

    Not so simple.. the trick is to know where to cut your hole first off, Then your troubles start..What is the shaft angle and...
     

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  9. parkland
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    parkland Senior Member

    Yes it certainly is explained as if it was the most high tech of machine assemblies.
    Biggest problem I found so far, is that google doesn't do very well cause 9 out of 10 websites I go to, I end up an a RC boat forum.


    So the tube get's welded in, cutlass bearing goes in, stuffing box goes on, propellor gets bolted on, and shaft bolts to transmission.

    And then I take it there are options like thrust bearings, and seals to go in the tube as well? How does that work when water is allowed throughout the entire tube up to the stuffing box?
     
  10. tom kane
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    tom kane Senior Member

    If you are really smart you should make your shaft drive adjustable (in a slot not a hole) so that it does not require crucial clearances and it can be easily adjustable if you want to change the shaft angle to add a bigger prop or some other alteration. Easier first time and no more expensive especially if you do not get it right first time.
     
  11. parkland
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    parkland Senior Member

    That is very interesting, and in the event of a collision of the propellor on a rock, could reduce damage greatly.
     
  12. gonzo
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    gonzo Senior Member

    KISS, that is the best system; particularly and underwater critical part of the vessel. However, there are people that choose complication for its own sake. To each its own.
     
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  13. waikikin
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    waikikin Senior Member

    It's simple to loft full size, then cut a small hole or slot, set up a string or wire to the proposed line of shaft & check sump clearances, bed positions & prop clearances etc etc, to cut the finished hole to accept the stern tube(pipe) do a string development in place-use dividers perpendicular to the string to mark inside forward & outside aft, center punch your line & cut, then weld in the pipe. Jeff.
     
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  14. tom kane
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    tom kane Senior Member

    Bugger the string trick these days, a cheap laser,why not.
     
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  15. tunnels

    tunnels Previous Member

    Thinks a little now and save a lot of hassles later !!!

    inboards ,motor and gearbox ,couplings thrust bearings and prop shafts , struts and all the gizmos at the back including rudder and shoe etc etc i always draw out full size in the garage floor or the drive way or a big flat smooth concrete place wven up on a wall if you lucky to have one long enought . saves lots hassles ,save lots of guess work and you can see in a instant what you have got and what you will get later when everything comes together to be fitted into the boat . scaling and making things smaller is never the same !!true acurate measurments ! nothings beats them !!. Same when doing outboards and changing transom etc .i do the full size !!you can get all the angles right the length of the shaft set to almost exactly the correct height plus you can see if you getting enough trim when its tucked under during take off and getting out of a hole and onto the plane i quick time . plus theres no "she'll be right mate "to find its doesnt fit when the motor gets hung oover the back to drill the holes for the bolts . :D:p
     
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