Custom outboard: 15-40hp w/25"+ Shaft?

Discussion in 'Outboards' started by salukikev, Jan 1, 2012.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    I know of 70 horse Johnnos were being extended by cutting the shaft, and welding in the extra length, but as you say metallurgy is a concern. Maybe there was enough spare capacity in those shaft diameters to absorb a loss, I'd guess if the driveshaft is a bit marginal to start with, it is problematical.
     
  2. Matt Gent
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    Matt Gent Junior Member

  3. salukikev
    Joined: Nov 2011
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    salukikev Junior Member

    Thanks! I'll definitely follow up with these guys! I had seen that 1st link previously, but not the 2nd. I think its interesting that I haven't been able to find a motor that has been retrofitted with one of these kits so far, and yet there is a large selection of conversion kits available. I guess my new question is what motor has the highest power/weight ratio in that range- then I will just add a kit to whatever that answer is.
     
  4. frank smith
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    frank smith Senior Member

    There is a kit for extending Tohatsu 25hp to 25" . This is the same engine as the Mercury and Mariner 25Hp .
     
  5. liki
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    liki Senior Member

    Atleast old OMC 2-cyl outboards had a 5" extension kit available. See e.g. here: http://www.evinrudeonlineparts.com/pages/OemParts#/Evinrude/E35ECSM_1980/GEARCASE_-_35/28299/41281

    I have a 1984 short-shaft 35hp that I fitted with leg from a 1994 20hp model. There are some very subtle differences like different size screws and maybe you'll one half of the gear shart connector from the engine and the other half from the leg, but if you are able to find an extension kit still from somewhere it should fit all 2-cyl 2-stroke for about between 1996-1986 for 20/25hp and 1996-1980 for 30/35hp. Browse the BRP parts catalogue, but the only source for the kit is likely ebay nowadays.

    EDIT; hmm. And check also the products from these guys: http://www.baymfg.com/ - Could prove to be much easier that way. :)
     
  6. frank smith
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    frank smith Senior Member

  7. salukikev
    Joined: Nov 2011
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    salukikev Junior Member

    I think I found it!

    Hi Guys,
    So after months of patiently waiting and browsing, and waiting and browsing, I think I finally found a winner. [​IMG]

    I think... I'm cautiously optimistic here as I'm still awaiting more serial or model info. I did talk to the owner though and he said it is a "military" outboard motor with an RD25 powerhead. The measured shaft length is a whopping 29"- which is great for what I'm doing. He described it as a very unique engine and he believes it to be a 2 cycle 4k rpm engine, and with a shaft length like that it is likely a custom midsection- it appears to be from the photo I have.

    The only hesitation I have is that it's old- probably 1960's or so. The ideal outboard for this project would not only have a very long shaft and a good amount of power, but also be as lightweight as possible. The weight also comes into play for shipping it here to Charlotte, NC. I forget what UPS's freight shipping limit is, but I recall last time smaller outboards were right near the limit.

    Any opinions on the viability of vintage outboards would be helpful as well as information as to how I can track down more specifications and/or info on this strange outboard would be tremendously appreciated! I'll write back with more pics and/or info as I can get it.
    Thanks!!
    -kevin
    **Not sure if that image posted correctly.. if not here is a link.
     
  8. whitepointer23

    whitepointer23 Previous Member

    looks like an old piece of crap, are you actually looking for the engine you need or 1 you can afford. i don't believe you even have a boat to put it on, well i can't find anything anyway, do you have pictures of this boat you are building. 20,25 & 30 inch are the standard lengths for outboards, every production boat on the planet is built around these shaft lengths yet yours is so special you can't get a motor to fit, give me a break.
     
  9. salukikev
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    salukikev Junior Member

    Wow whitepointer23- you're awfully critical, aren't you?

    I wouldn't mind looking for one that fits all my criteria- not sure what's wrong with that mindset...
    Anyway- as the motor is the most critical and most challenging component to find, I'm starting there and working around the outboard I end up with. As I explained early on, I was looking for a very long shaft, and high power to weight ratio (2 stroke). Finding a shaft like this on a motor in the range of 20-50hp is next to impossible and that's how I ended up here. If you have any constructive suggestions that are a little less condescending, I'd love to hear them.
     
  10. whitepointer23

    whitepointer23 Previous Member

    i probably was a bit harsh but i don't understand your problem, if you can use a 25 " why haven't you got one, they are very common in omc brands in that range. that old thing you are looking at will probably crap it self before you get much use out of it. what is the boat you need it for, put up a photo or drawing so people can understand what you are doing.
     
  11. salukikev
    Joined: Nov 2011
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    salukikev Junior Member

    Well, I'm not looking for design/engineering advice at the moment, just a motor. It takes some trouble to explain nuances of the design and I was trying to keep this a simple post. There have been some kits mentioned, but I was hoping to find either an already kitted motor or a factory motor with an odd combination of specifications like this.

    You say that these OMC's are common with 25" shafts in the 20-40 or 50 range, but I think you'll be hard pressed to link to one. Finding a 29-30" in that power range is nearly impossible from what I've seen.

    Earlier in this thread Michel Pierzga kindly linked the only motor I have seen sold stock in that power range with a 25" shaft. The trouble with that motor is the weight (223lbs dry), and the expense- brand new $5k with a warranty that would be voided w/modifications.

    This project benefits from:
    A) 20-50hp
    B) A 25" shaft or longer
    C) A low weight

    all requirements of which this recent motor appears to at least potentially meet. Its true that I'm hesitant to integrate such an old motor, but that's why I'm here asking about it.

    At the risk of taking this thread off topic, I will tell you that this is for a small hydrofoil craft- quite different than your typical boat, as it will be fully out of the water except for prop & foil when in use. This is why a 29" shaft length is of great interest, even if I need to rebuild the power head.

    I have some tentative CAD designs currently, but they are generally irrelevant until I can scan in or CAD in a suitable outboard to get things started.

    I hope that explanation helps justify the particulars of my motor choice.
    Thanks again for any help!
    -k
     
  12. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    How much are you willing to spend for the motor?

    What capabilities do you have for mechanical design and fabrication?
     
  13. salukikev
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    salukikev Junior Member

    Dcockey:
    1. I feel like I should be able to find something under $2k. Obviously the more ideal the more $. Other than the age of this recent candidate, it so far seems pretty close to ideal.

    2. I am a design/engineer. 4 days of the week I work at a product design firm, the 5th (& weekends) I run my own business doing the same invention/design work. Both have CNC operated mills/lathe and mig/tig/spot welders. The former has a sponsored hydraulic bender/notcher & laser. Also, although I'm not super experienced, I'm looking to improve my fabrication with composite layups.
    *Also- I have a handy copy of Locus
    :)
     
  14. whitepointer23

    whitepointer23 Previous Member

    i had an 18 hp evinrude with an extension to 25" and a friend had a 15 evinrude with a 25" kit, i also sold a 12 hp tohatsu last year with a 25" leg, i have seen a lot of omc extension kits fitted. maybe they were more popular here. i think these kits were available for yacht auxillary engines. 30" legs are in the large size outboards, 150 plus.
     

  15. salukikev
    Joined: Nov 2011
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    salukikev Junior Member

    I guess when I originally posted this thread I had lowered my standards to include 15hp out of desperation. Really I was looking for something over 30. None of your examples are over 20 which was my more recent statement. I realize the 30" are typically for the 150hp plus- and that is way too much for this craft. Those motors are also typically 400+lbs.

    In contrast- tonights research suggests that this recent find is:
    40hp 2 stroke
    131 lbs
    Approximately 30" shaft.

    So- if I can confirm all that- its damn near ideal with the only exception being the age. I'm neither an expert boater nor particularly familiar with vintage outboards- and that's why I'm here.
     
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