Can i replace Inboard with Outboard on shaft

Discussion in 'Inboards' started by Brian Blake, Dec 26, 2017.

  1. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    I've recently purchased this (images below) 27 foot Ship Builders. Its a beautiful boat and is solid as a rock albeit in need of a paint tidy up and some minor TLC. Aside of one major problem.

    The diesel inboard (photos attached) has overheated at some stage and died. I haven't yet investigated what state its in but its also very "wet" as in the whole boat smells of Diesel and i can see Diesel sitting on the surface of the bilge water. It looks like its generally been hard worked i think so i'd feel more comfortable with it coming out.

    Is it possible (i guess anything is possible but what problems would i anticipate) to remove the inboard and install an outboard in its place but engineered to attach to the prop shaft at the spider gear that meets the current gearbox. I'm aware i would need an engineer to make the shaft etc. But my worries include things like weight distribution as that engine looks mighty heavy, what about the prop ratio given it would be running 1:1 without a step down? Is that do-able.

    So basically has anyone ever seen this done? This is my first larger boat and i really love this style, i got it for a song because someone wanted it gone so i don't mind spending a little to make her look loved again.

    Also can anyone confirm for me what that engine HP is? I looked online and seen everything from 35 to 140hp!

    Thanks
    Brian
     

    Attached Files:

  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    If you positively ID the engine, you can get the information about it from several online sources. Find the engine ID number and you're good to go.

    Yes, you could do what you'd suggest, but it would be a real hodgepodge and not especially efficient, likely breaking things all the time as you sort though the issues, as they appear. So, you have a dead engine, but you also have a transmission, manifolds, plus a host of other bits and pieces, some application specific that aren't toast, right? Why would you toss all this over the side, for some weird home built rig?

    If the engine got hot, it can likely be rebuilt, unless you really cooked it, at which point you can swap out parts to make another, similar, but healthy engine work. That hull looks like it's a full plane design, so you'd have a much more than 35 HP in there, though I could be wrong. What is the year, make and model? Mt point is, why re-engineer stuff, when all you need is a rebuild or engine swap. If it's a matter of costs, well there's nothing about "yachting" that is inexpensive, particularly when diesels are involved.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I think that is the 3.8 liter engine, but they also made a 3.4. The maximum power was 60HP.
     
  4. PAR
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    PAR Yacht Designer/Builder

    I find it hard to image that hull being powered by a 60 HP engine. Have you any out of the water pictures?
     
  5. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    27ft, 60 HP makes a lot of sense. Thats only about MacGregor /motorsailor standards.
     
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  6. PAR
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    PAR Yacht Designer/Builder

    Does the profile provided above, give you any hint this might be a displacement mode vessel? Me neither . . .
     
  7. Ike
    Joined: Apr 2006
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    Ike Senior Member

    Besides having a hodgepodge (as PAR said) you will also be introducing two other problems. You will be switching to gasoline which is a much more volatile fuel than diesel. So now you have to start thinking about preventing fires and explosions, ventilation systems, ignition protected electrical systems and the fuel system, as well as Carbon monoxide. All issues associated with gasoline, that are not associated with diesels. Plus that, outboard engines are not designed to meet standards for fuel electrical and ventilation for permanently installed gasoline engines. Dealing with those issue plus the problems of adapting something to a drive designed for a inboard diesel will raise the costs to the point where it would be far simpler and cheaper to buy a rebuilt diesel, or rebuild this one. Are you sure this engine is ruined? The engine in my boat sat for 10 years out in the weather, and after some relatively minor repairs it fired up. Have someone who knows diesels take a good look at it. It may be salvageable.
     
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  8. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Thank you all.

    I only just bought the boat, and its my first beyond "fizz boat" status but i loved the hull shape and it was going cheap with the stuck motor so i rolled the dice a bit. The hull is in good condition and very little water on board so i'm really just wrangling with the engine and some cosmetic scenario stuff now.

    I was told by the previous owner that it "got hot and now wont turnover" and its sitting on the water at the moment so is a little hard to investigate the engine too far. Given the amount of diesel i could smell when on board and the slick in the bilge water, when combined with previous owners comments about the motor being a bit "sketchy" i'm of a mind to replace it with another diesel for all of the safety reasons above. My kids will sleep & fish on this thing, it needs to be safe. I couldn't get enough space to see the engine serial plate but i can tell its a pretty messy patchwork of running repairs which make me less attracted to recondition it. As best i can tell by researching online its made by the same engine guys (Leyland?) that made the London black cab engines and is them marinsed. I think its a 2.2l diesel which runs about 60hp if I've tracked down the right kind of engine.

    I'm currently trying to form my plan of "outcomes v expenditure" to try and minimize hard stand time. You've all given me some very good, practical advice which i will follow.

    Moving the question slightly i'm looking at a Nissan Diesel LD28 which has previously run a Sternleg (so has no gearbox on it). Non turbo developing about 90hp. Am i likely to be able to bolt the existing gearbox to the flywheel/block or is there some sort of transition plate can be purchased to map mounts for the gearbox to the flywheel? I guess in a backwards kind of way i'm asking are all/most marine gearboxes the same mounting pattern at the flywheel? Also, can i just put 90hp on whats presumably a 70 odd hp gearbox safely?

    I've worked on cars, motorbikes and truck engines over the years so i'm fairly comfy with mounting/wiring/ etc, its more that i know very little about the application specific things like marine gearboxes, but i'm keen to learn.

    Thanks for all the advice so far and any further received.

    Thanks
    Brian
     
  9. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Can i rather ignorantly check here,

    As a displacement hull it would not be expected to plane (e.g lower horsepower needed?) and as a "full planing" would that imply that it should get up on the plane? As that seems a stretch to me for a boat that big and heavy?
    I'm completely out of my depth (pun intended) as far as the hydrodynamics part of how a hull planes so feel free to correct me.

    As far as good dry stand photos, unfortunately no, i don't yet have any useful hardstand photos other than the one attached.

    Thanks again.
     

    Attached Files:

  10. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Your're right the image is poor, but I can see enough to tell you it's a full plane mode vessel and yes, a boat this size can plane (easily). You'll need a couple hundred HP, which a small block can easily provide, even an L4 or V 6 can do this.

    No, different engines use different bolt patterns for the bellhousing and different gear ratios in the transmissions too. If you stick with the same output, you'll likely have an ill handling beast, as you'll need a minimum of a 150 - 170 HP (depends on weight) to get her to act properly. There's not much worse than a grossly under powered full plane hull, in terms of maneuverability and handling. There are lots of 4 cylinder 150 HP diesels around, though you should find one with the appropriate bolt pattern for your transmission. You should also check the transmission, to see if it can handle this power and if it has the right gear set. With high 100's to 200 HP you should see speeds in the low to mid 30's which is pretty good for a puppy of that size. With 60 HP, you'll see much less than 10 MPH (7 - 8) and she'll wallow around like a cat on ice.

    The first thing you should do, is clean up the bilge and sort out some start wiring, just to see if it'll turn over. Diesels need fresh batteries for this (lots of compression). If it'll start, you might as well sort out why it doesn't. Often it's simply a maintenance issue, like pumps, injectors, filters, bad wiring, etc.

    In all honesty, if they said it was "sketchy" it's probably spent and you should look for another engine/transmission setup, just to be safe. It might be just a spent engine, but would you like to go to the effort to replace it, just to find the transmission is in a nearly identical condition? You can also go full gas, which is way cheaper and much easier to find parts for too. The engine compartment looks tight, so maybe a straight 6 is an option. Typical V8 engine bays have about 24" between the two stringers, which is enough for the block to drop down on it's mounts. If it does, the venerable SBC is a logical choice, given availability and pricing.

    Without better pictures and a positive ID of the year, make and model, it's hard to suggest where to go and what will fit or what she might need. It's a bit like asking what to do with my car that has a spent motor, without knowing what it is, the year, etc. Get in there with a mirror find the ID tag and write it down, ditto the transmission.
     
  11. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Thanks,

    Have you any thoughts on the previous comments about the safety of gas on board? That rattled me a bit and logically makes sense.
    I think i'll get out to it this weekend and spend a good amount of time climbing over it.

    Thanks
    Brian
     
  12. Ev1
    Joined: Feb 2017
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    Ev1 Junior Member

    I think you are thinking this all wrong You want an out board as a inboard Mmmmmmm. Why not do what most do to repower a inboard with an out board Build a pod hang it off the back nearly all petrol related problems go away
     
  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    100's of thousands of boats are gas powered with few mishaps and those that do are nearly always because the owner screwed the pooch in maintenance, up keep, etc.
     
  14. Brian Blake
    Joined: Dec 2017
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    Location: Auckland, New Zealand

    Brian Blake Junior Member

    Thanks, hoping to get on it this weekend and do some climbing.

    When you suggest SBC is this an abbreviation for "Short Block Chevy" or have i missed something? Also where is good starting place to look for engines online? in New Zealand we have a local ebay equivalent but i'm either getting 100hp our 400hp, neither of which really fit the brief.

    Thanks again
    Brian
     

  15. rasorinc
    Joined: Nov 2007
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    Location: OREGON

    rasorinc Senior Member

    try michigan motorz they should be able to ship to you.
     
    Last edited: Dec 31, 2017
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