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53 ft cruiser with outboards

Discussion in 'General Yachting Discussion' started by Edge cruiser, May 20, 2018.

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  1. Edge cruiser

    Edge cruiser New Member

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    May 20, 2018
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    Location:
    Australia
    Hi guys
    Im new to this forum
    As i can not find any data on the net regarding my current project
    Im after as much useful info as i can get in regards to installing outboards on to my brand new 53 ft fly bridge cruiser
    This vessel was originally designed for 700 hp twin screw application but never installed
    But due to the cost of purchasing the engine's and gearboxes and all the under water gear and then to have them installed in on my vessel in my location was not a viable option
    Thus my current position
    I have had the transom modified to accept up to 4 x outboards with centres set at 660 mm( but possibly can go wider) and 30 in legs
    The vessel has a semi displacement hull which has a 45 ft water line with 5.1 mt wide beam and a displacement of 24 tons if i went with the inboard installation
    But i will be reducing this by roughly 4 to 5 tons if i put 4 x outboards on
    Im just after some useful feedback as to the requirements and limitations i am going to face moving forward
    I thank you all in advace for your assistance
  2. YachtForums

    YachtForums Administrator

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  3. Capt J

    Capt J Senior Member

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    And that was a customer of mines, old boat before the current guy had rigged it with outboards.....LOLOLOL
  4. maldwin

    maldwin Senior Member

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    Dark Harbor Me/ Hobe Sound Fl

    Huckins built a 53 footer with outboard power for a client in the seventies, but she has since been converted to inboards.
    Best,
    Maldwin
  5. Capt Ralph

    Capt Ralph Senior Member

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    I remember her. Had 4 OMC SeaDrives. It did run well.
    But remember, Ole Hucks have little deadrise and draft. Near a box with a point on one end.
  6. Oscarvan

    Oscarvan Senior Member

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    That's a lot of weight to (re)move from the center of buoyancy/just aft of COB to WAY out back. I would speak to a naval engineer to do some calculations here. Now, HP for HP you would indeed save some weight here. In fact you could end up having to add ballast somewhere/move tanks forward. And, the sugar scoop on the back would probably have to have volume ie be a pod to provide some buoyancy. It is regularly done on smaller boats to free up space in the cockpit/remove PITA inboards/stern drives. Then there's the issue of vertical travel of the stern/swamping on a boat that would/could go on bigger water. Again this needs serious MATH. The laws of physics ALWAYS apply.

    So, to do it RIGHT may or may not be a savings over a conventional installation. Of course if you're extremely talented and have the tools you could do it cheaper.

    And then..... how would it look. But that's for another thread.
  7. Edge cruiser

    Edge cruiser New Member

    Joined:
    May 20, 2018
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    Location:
    Australia
    Thanks Oscarvan for your positive input
    My ship wright and i have already had this discussion about the distribution of weight
    As for hp diesel engines are rated at the flywheel and outboards are rated at the propeller as you would be aware
    We are going to gain some 350 to 400 hp over the conventional twin 700 hp inboard application if i went with 4 X 300 hp outboards
    And we all know how noisy those inboards can be at at W O T
    As this is a new build and we have a clean slate to work with
    We can add or move ballast around till we get the correct formula
    With the subject of swamping
    I dont think that will be an issue because we have redesigned the transom to accept 30 in legs buy increasing the height some 370 mm from where it was and created a well where the last platform / step use to be and installed 2in drain holes at each end to siphon away any backwash or water that may get onboard
    As the vessel was designed with plenty of freeboard at the transom to accept a platform / marlin board and two steps up to get to deck height we have only lost one step to accommodate the outboards
    We have a clean hull to start with as mentioned This is a new vessel and never seen water so we dont face the problem of patching up stern or rudder tubes or the task of removing and patching underwater gear and removing the engines and gearboxes
    I have enrolled the services of a first class Shipwright
    His work is exceptional and does not look like it is tacked on as some of the photos i have seen in reply to my post
    I am still keen to discuss and eager to listen to anyone with some positive input as we are still in the build stage
  8. Capt Ralph

    Capt Ralph Senior Member

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    My ship wright and i have already had this discussion about the distribution of weight
    I'm sure he is a great guy. But you did not call him an marine architect.
  9. Edge cruiser

    Edge cruiser New Member

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    Hi capt Ralf
    Thanks for your input
    I will make arrangements to meet with a navel architect to discuss the issue of weight distribution on my vessel
    As I have be dwelling on this for some time I did have a plan in mind to start with one half the weight of the inboard motors and all attachments as balast ( water in plastic 44 gallon drums ) just aft of mid ship and add or subtract as needed
    Now I will take your advice capt ralf and have words with ano architect prior to launching
    Again
    Thanks for your input