Inboard to outboard conversion question

Discussion in 'Boat Design' started by Alex Clifford, Nov 10, 2021.

  1. Alex Clifford
    Joined: Nov 2021
    Posts: 3
    Likes: 1, Points: 3
    Location: Virgin Islands

    Alex Clifford New Member

    So we have a 1999 25' Fratelli Aprea. Owner wants to remove the two 150 hp Yanmar inboard. With those gone, I would have to construct a mounting platform off her stern stable enough for at least two 150 hp outboards.
    I have many concerns. Mostly on what her waterline and displacement will be, how she will handle underway and so on and so forth. I would love to hear back from you salty fellows!
    Oh and we're out in the virgin islands so our resources are limited... besides rum, sand and beautiful women.
     

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  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    I'm disappointed in the small picture I don't seem able to expand, more disappointed that there are no pictures of the beautiful women ! All is not lost however, as there are a few pix on the internet, though it is hard to get a clear view of what the underbody looks like, and it seems this boat has been "dummied" to look like a traditional Mediterranean boat, but is a more modern type of hull. The lack of a flat transom seems likely to make your idea a little harder to execute.
     
  3. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Welcome to the Forum Alex.

    Is your boat a Fratelli Aprea 750, like the boat in the link below?
    1999 Fratelli Aprea 750 Antique and Classic for sale - YachtWorld https://www.yachtworld.com/yacht/1999-fratelli-aprea-750-7957411/

    And do you have the same Yanmar 4JH3-DTE engines?
    Why does the owner want to remove them - are they both totally shot?
    Not worthwhile trying to re-build them?

    It would be a very big job to convert to O/B motors instead.

    Edit - I thought that these folk were in the USA, but they are in Indonesia! So not much use sadly.
    Here is a company in the USA selling new Yanmars - it might be easiest (and cheapest) in the long run to simply buy a pair of new diesels (and then you can keep the old ones for spare parts?) ?
    New YANMAR 4JH3-DTE Inboard Engine 125 HP - Diesel - SALE !! https://www.outboardisland.com/new-yanmar-4jh3-dte-inboard-engine-125-hp---diesel---sale
     
    Last edited: Nov 11, 2021
  4. Alex Clifford
    Joined: Nov 2021
    Posts: 3
    Likes: 1, Points: 3
    Location: Virgin Islands

    Alex Clifford New Member

    Thanks for welcoming me to the forum!
    That photo you linked isn't the same. Close. I believe that's the next size up. 32' with the fixed half cabin top.

    She does have the hull design. I'll include a picture of one that's not in the state of repair she's in right now.

    I'll include a copy of the email we received from the yanmar distributor. He basically said our yanmars were out of date and impossible to find in our location. I'm curious to see if we could get new replacements from the link you provided.

    Our thought process leading up to O/B was basically if we had to spend a pretty penny on new inboards why not go for more horsepower with outboards.

    We have the 2 Yanmar inboards all disconnected and scheduled to be pulled out this Saturday.

    I still have so much work on the new decks, toe rails, exterior teak that wraps the top of hull(just for looks)... I also have to make a new head, v birth, and kitchenette. All things I know I can do since I spent 4 years at Hinckley as a finish carpenter. But this transom extension is something out of my wheelhouse.

    All doubts and speculations are welcome bouys! SmartSelect_20211111-125633_Chrome.jpg Screenshot_20211111-132548_Gmail.jpg Screenshot_20211111-132611_Gmail.jpg
    20210630_104928.jpg 20210630_104928.jpg
     
  5. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Re the link in my previous post re Outboard Island - maybe they can sell new Yanmar 4JH's because they don't have to subscribe to such strict emissions regulations there?
    There again, here is a company in the UK offering a 110 hp 4JH for sale in England for GBP 13,000 - this includes VAT, so you could knock off the 20% VAT and it would then be approx GBP 11,000.
    But this is still a lot more than $9,300 (I presume that this is US$) from the outfit in Indonesia.

    I still think that your best bet will be to try to find a suitable pair of replacement engines, rather than doing a lot of retrofit work to convert her to outboard motors.

    These folk are in St Thomas, and they can sell you a new 4JH 110 hp 'for export / replacement only' - and you are replacing yours, so that should not be a problem?
    Yanmar 4JH5-HTE Offshore Marine http://www.offshorevi.com/engines-outboards/yanmar-4jh5-hte/
    Or have you been in contact with them already?
     
  6. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    The boat is simply a horrible idea for outboards. There is limited transom area; the transom is almost certainly too weak; the load paths of stringers in the hull uncertain, but likely wrong, a custom built pod or bracket would be expensive to design and fabricate; outboard rigging could be trouble or by wire would cost like 3k more..
     
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  7. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    +1 what Fallguy says above - and also, any appendage that you attach onto that nice curvy stern is going to look seriously ugly, no matter how hard you try to tart it up.
    Do your maths, work up a rough estimate for your hours and the cost of materials to modify the stern, add on the cost of O/B motors, a new steering system, and a new throttle / gear control unit - and then compare this total against the cost of buying two new Yanmars.

    However - you have not actually said what is wrong with the existing Yanmars.

    'Out of date'?
    The Yanmar 4JH series were / are very popular engines - I am sure it is still possible to obtain parts for them.
    That Yanmar Distributor might have ulterior motives - he probably wants to sell you some new engines.
    Even if the engines themselves are knackered (how many hours are on them?), you might be able to salvage the gearboxes?

    Edit - more random thoughts.
    I presume that the owner of the boat is a good mate of yours? How long has he owned the boat - or has it just been purchased?
    If he has had it for a while, have you been out on the boat with the current engines working?
    If so, what is the performance like with these engines?
    Re putting outboards on, what speed were you hoping to achieve with (say) 2 x 150 hp motors?
     
    Last edited: Nov 11, 2021
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  8. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Not really a boat the would suit outboards, I would think, after watching a couple of youtube videos, this boat appears to be a semi-displacement type of vessel with no great pretensions to being a speed machine, diesel power seems most suitable, big outboards beyond about 120hp don't run gearboxes that would do justice to such a hull form. If the diesels are about to be pulled out, why not rebuild them ? I think you are on the wrong track if you see it stepping up in speed with a couple of outboards, it is not the hull for it.
     
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  9. Alex Clifford
    Joined: Nov 2021
    Posts: 3
    Likes: 1, Points: 3
    Location: Virgin Islands

    Alex Clifford New Member

    Hey guys! Just wanted to thank you for your opinions. After the owner read them he agreed that we should replace the old Yanmars with new ones.

    We pulled them out yesterday flawlessly! Usually pulling engines isn't a big job, but when the boat is tucked up on a hill on the side of an island it makes it more difficult.
    There's nothing easy about island life-price we pay to live in paradise.

    But I'll keep you guys posted on this rebuild. I'll come to you guys first with any future questions or advice. Thanks guys!
     

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  10. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    Have you decided yet which type of Yanmar you will be installing?
    What were the cruising speed and maximum speed with the old engines?

    If you are happy to go a bit slower (and be more fuel efficient), then you could perhaps fit a pair of naturally aspirated Yanmar 4JH engines - these are around 56 hp each.
    One advantage of these is that you might find some available in the BVI's still, re all the wrecks that Hurricane Irma (or was that Maria?) created a few years ago - these 4JH engines were standard issue on many Beneteaus and Jeanneaus around 40', and also on slightly larger cats, and many boats were destroyed in the hurricane.

    Please do keep us updated re the re-build, and subsequent sea trials.
     

  11. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Wise decision. The boat can be so beautiful as designed.
     
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