Buying or Building a Z Drive?

Discussion in 'Propulsion' started by Pceditorpro, Dec 3, 2018.

  1. Pceditorpro
    Joined: Dec 2018
    Posts: 2
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    Location: Massachusetts

    Pceditorpro New Member

    I'm getting ready to start building my first boat. It will just be a 24ft flat bottom skiff. Mostly used for recreational lobster fishing and helping friends move some docks around. When I started studying for this I decided on a few things first I wanted more of a learning opportunity then just buying things off the shelf like a simple outboard and after repairing boats for a living for the last 7 years I may be a little paranoid when it comes to reliability. I wanted to build twin Z drive pods that will be set off the stern like an outboard would be placed. I was thinking of powering theses via shaft driven. I have read a lot about people using hydraulics but they seam to only be worth it on something much bigger. For power-plants I was thinking of using 2 350 Chevys I was given by a friend when he moved. They just got back from the machine shop ready to be assembled. This is probably way to much power but I have them and trying to find parts should be relatively straight forward. I guess the first thing to ask is where is the best place to find information on Z drives for this application? Do they sell something that I can use or do I need to make something? If I need to make them are their any good plans to work off of? In general what do you thing? I'm kinda looking to just bounce some idea around on this.
     
  2. Barry
    Joined: Mar 2002
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    Barry Senior Member

    and why not just an IO, especially if you are going to mount them on the stern
    No rudder, vectored thrust with the turn of the outboard unit

    Volvo even has a computer controlled joystick positioning device to help with docking if that is why you would want a Z pod that turns.
    In a 24 foot flat bottom boat, 600 plus horsepower?
     
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    :eek: One of those engines would be far too much for a flat bottom 24 footer. And unless they are marinized, simply forget about that power option ( a single 350 )
     
  4. Barry
    Joined: Mar 2002
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    Barry Senior Member

    What is the beam? If it is a trailerable width of 8 feet, it will make the installation of twins difficult plus hard to work on.
    A 5.7 set up with outdrive is about 1100 pounds, a pair of them 2200 pounds, in the back of a 24 boat with an 8 foot beam, this is excessive.

    Unless your engines already come with the marinized components required to make the engines legal and safe, the cost to complete these blocks will be excessive.

    It appears that your selection of twin 350s is revolving around the fact that you have been given a couple of blocks, perhaps you are trying to build this boat as economical as possible.
    So on a tight budget, an option would be as follows. Locate 1 (one) used stern drive assembly from someone who has upgraded his boat that has a worn out engine. Craigs list, kijiji,
    etc and install one of your blocks into it, rebuild the stern drive portion, (depending on the extent of the rebuild maybe 3500 US). If you want a get home engine, install a 25 hp Yamaha, they
    have a new lightweight version of them, I think about 120 pounds.

    Marinizing a 350 engine,
    You should have bronze/brass frost plugs, marine starter, carburetor, fuel pump, distributor, flame arrestor, alternator, raw water pump. Generally, the cam is ground for marine
    applications as you are looking to produce more horsepower at lower rpm, ie higher lift/or duration. This stuff is expensive and that is the reason I suggested the used sterndrive set up
    as these components will come attached

    If you are going ahead with two engines, against advice, Add to one engine the cost to make it a reverse rotation engine, timing gear set, distributor, Lots of bucks here

    An expensive heat exchanger, not absolutely required but the best way to cool your engine.

    And flat bottom. We have built many 12 degree jet boat hulls to be able to run in shallow water, but have occasionally taken them into larger waves and even at 12 degrees in short even 2-3
    foot waves the ride is kidney killing. Why would you want a flat bottom?

    We had a 10,000 pound 26 foot cabin cruiser back around 1981, 10 foot beam, with one 5.7 stern drive, suspect about a 22 degree deadrise, this boat would cruise easily at 28 knots
    at about 3300 rpm. One engine, heavy boat, full cabin, black water, regular water, 140 gallons of fuel,

    Anyway you said that you wanted to bounce some ideas around and with a flat bottom boat you will,
     
  5. Pceditorpro
    Joined: Dec 2018
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    Location: Massachusetts

    Pceditorpro New Member

    Sorry for the late response I had to finish finals for school.

    Design wise I got the idea of a flat bottom because a good 70% of the harbor here is flat bottom. At low tide you can basically walk around the harbor on the mud except for a few places. Making a flat bottom boat nice for both leaving on a mooring instead of a trailer and having less worry about draft. I like the idea of the stern drive system the only reason I was looking at Z drives was it would be something different and sounded like something fun to engineer. Placement of the engines was going to be about a 1/3 off the stern so the weight would be more centered in the hull. I wanted more of a tug boat then a speed boat. Something I can put to work on the weekends moving docks, floats, barges. Twin 350s looked like a good idea at first because they are widely used in the industry so parts will be easy to find.

    Barry you definitely have suggested up a lot of things that I did not think of and need to. The idea of stern drives is something I never really though about but now I really like the idea. Other then cost to build and weight is there any other reason to not use twin 350s? I know I will burn more fuel. Just out of curiosity saying cost was not a factor what would be reasons against? I know fuel would double and hull construction would be a priority because of the forces involved with that kinda powers, size, and weight. But if you took your time it could be done. I'm just curious the books I got spent a ton of time on hull design and almost nothing on propulsion other then a few pages on sails.

    Sorry to be the newbie asking questions like this. I am definitively seeing holes show up in the plan I had in my head as it makes it's way to the next stage of design.
     
  6. Brett Fiddes
    Joined: Jan 2019
    Posts: 3
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    Location: Melbourne Australia

    Brett Fiddes New Member

    Hi was reading your post after trying to search prop calculator for surface drives
    For whats worth I have just bolted in Z-drive using Hallcraft/or Casale these come in parallel drive /Z-drive configuration
    Im running Arneson surface drive ASD6 then Z-drive which lifts the 1410 universal up 4" height then to Crash gearbox (F/N/R) and then to 502 ci Chev
    the boat is 21.5 ft ski boat
    Should be in water within 6 months, most of heavy engineering has been done, just have to tidy up outside of hull, and start fitting out boat with parts
    This was non factory boat, so everything is new
    Boat used to have a large outboard on back
    will try and post some pics of the Z-drive shortly
    Happy New Year
     
  7. xrudi
    Joined: Jul 2003
    Posts: 146
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    Location: Philippines

    xrudi Rudi Scholz

    The prop calculation for surface drives were published about 20 year ago ago. It is all there, Contact me.
    Happy New Year
    Rudi
     
  8. Brett Fiddes
    Joined: Jan 2019
    Posts: 3
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    Location: Melbourne Australia

    Brett Fiddes New Member

    Rudi
    thanks for your message, I'll drop you a email latter, very interested find out anything
    The ADS6 uses 19 spline, with Z-drive I'll be running RH prop
    Have been collecting a few over the years,

    actually boat has similar fine bow, and stakes to levi design
    Someone had passed a comment that the boat could of been shortened to 21.5', but who knows?

    Been trying to track down he built the FRP boat in Australia but given up
    just want to finish it
    there was a wooden levi designed hull used to race here in Melbourne a few years ago owned by colin pratt used to run 351" ford engine (managed to find a older advert)
    There used to be a contact here some years ago that was contact for Levi designed boats as saw advert showing 26' with staggered twin engine setup (advert attached)

    managed to find pic showing Z-drive connection between gearbox and ASD6,

     

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  9. xrudi
    Joined: Jul 2003
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    Location: Philippines

    xrudi Rudi Scholz

    Yes this one is of Sonny's Delta Designs.
    This Arneso use splines only to make things more complicated for the customer and make some more money. Arneron buys the propeller from Rolla. Arneson has no experience about propeller!!

    Cheers Rudi
     
  10. Brett Fiddes
    Joined: Jan 2019
    Posts: 3
    Likes: 0, Points: 1
    Location: Melbourne Australia

    Brett Fiddes New Member

    Rudi
    its a pity there is no manufacturing ID tag on the boat that Im rebuilding, as had to rebuild stringers and transom
    haven't put the boat in water yet, so not sure how its going to sit, although front of BBC is 1.3m from transom and overall length is 6.1m
    When I moved boat onto trailer managed to get the the boat rocking on sling so was able to determine where the centre of gravity was.
    Was going to fabricate 2 saddle tanks up and try and carry 100 litres fuel each side, but concerned where these will be positioned to balance out boat

    So you advising the 26' boat in advert is Delta design?
    cheers
    Brett
     
  11. xrudi
    Joined: Jul 2003
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    Location: Philippines

    xrudi Rudi Scholz

    Hi Brett,
    Yes, if the transom is the wides part, we would call it Delta. This is to get the buancy, where the weight is. (at
    the back of the boat)
    Have fun.
    Best Regards
    Rudi
     

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  12. xrudi
    Joined: Jul 2003
    Posts: 146
    Likes: 4, Points: 28, Legacy Rep: 75
    Location: Philippines

    xrudi Rudi Scholz

    Hi Brett,
    I did not get a reply. The subject is closed?

    Best Regards
    Rudi
     
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