Which Outboards to power a TinyHouseBoat?

Discussion in 'Outboards' started by Tom Peach, Oct 1, 2020.

  1. Tom Peach
    Joined: Oct 2020
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    Tom Peach Junior Member

    I am looking to self-build a Tiny House (timber frame) on a pontoon and am wondering what size engines I would need?
    From the research I have done so far it appears I need to be looking at "High Thrust" types, would you agree?
    The boat will be 10m in length by 4.0m beam (32'6"x 13' if your stateside)
    If it makes a difference I was thinking to use these pontoon floats with some sort of metal frame on top to support a traditional timber frame construction single level house.
    I was thinking either 4 x PT01 type floats or 3 x PT06 type
    I expect the finished weight to be around 4000-5000Kg (8800-11,000lbs)
    I know I need more than one outboard but would two work on a pontoon style boat of this size and weight? If its any consolation, the boat will not be used to travel much at all as it will be used as an AirBnB for vacation rentals so will stay put in a marina berth and only be moved to refuel and pumpout waste. The marina is a coastal one and I can't imagine this vessel being very 'seaworthy'. So I guess its not like it has to achieve any respectable speed, just enough to maneuver round the marina.
    Maybe a couple of High Thrust Yamaha's or is there an outboard with a higher gear ratio / larger prop that might be better?
    What are your thoughts?

    I have included a rough floor-plan for anyone interested.
     

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  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Welcome to the Forum Tom.

    Some rough calculations - if we just consider the mid-section PT06 floats : they are 0.83 m. long, and have a load capacity of 206 kg at the maximum recommended draft of 0.4 m.
    12 of these floats would be 9.96 m. long, giving a load capacity of 2,472 kg.
    If you have three pontoons, each comprising 12 floats (36 floats in total), that gives you a load capacity of 7,416 kg.
    Re your finished weight estimate of 4 - 5,000 kg, I guess that this is with tanks empty?

    You mention that journeys under power will only be used to refuel and to go to the pump-out dock to pump out waste.
    Would it be feasible to have a composting toilet instead of a conventional marine toilet?
    For example - Welcome to Strumpet and Trollop! For your glamorous composting toilet needs https://strumpetandtrollop.com/
    It might be more 'user friendly' (less likely to get blocked up by guests not accustomed to marine loos) than a marine loo?
    I think it separates pee from poo - would you be allowed to discharge pee overboard?
    Similarly grey water from the sinks and shower - does this have to be sent ashore, or can it go overboard?

    If it is ok for pee and grey water to go overboard, then you would not need to travel anywhere, apart from when the boat has to be hauled out, and then it might be easier to engage the services of a marina launch / tug instead?

    Some marinas in the UK are very fussy about 'Liveaboards' - if you have people staying on board semi-continuously for months at a time, would this be regarded as 'liveaboard'?

    It might also be useful asking your question on the YBW Forum in the UK -
    Practical Boat Owner's Reader to Reader https://forums.ybw.com/index.php?forums/practical-boat-owners-reader-to-reader.13/
     
    Last edited: Oct 1, 2020
  3. fallguy
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    fallguy Senior Member

    Better check the weight calcs. Most times people put houses on toons; they sink the toons really deep and then come back here asking for help.
     
  4. fallguy
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    fallguy Senior Member

    Most boats that size are running a single 50-115 4 stroke. Mostly depends on wind expectations.

    I ran a 42' boat this summer and it had a 90 horse suzi.
     
  5. bajansailor
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    bajansailor Marine Surveyor

    +1 re Fallguy's suggestion to check your weight calcs - you need to do much better than to simply estimate that it will be in the range 4 - 5 tonnes.

    You should try to do a detailed breakdown of the weights of all the components that will be used in building the house on the pontoons - as well as all the outfit items, provisions and stores, people, water, fuel (if you do have an engine)......... it all adds up. And if you go beyond the recommend maximum of 0.4 m. draft on the pontoons you might find yourself in a bit of a sticky situation.

    One disadvantage of having an engine on your boat - unless you disable it, or chain the boat to the dock, there will be times when your Air BnB guests will decide that it is time to take the boat for a cruise (probably on their return from the pub, after having a few drinks).

    Your floor plan looks neat - would you have a convertible sofa in the living room, to effectively have beds for a maximum of 4 guests?
     
  6. Tom Peach
    Joined: Oct 2020
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    Tom Peach Junior Member


    Firstly thanks for the reply.

    I wonder if your name (Bajan Sailor) means you are from or in Barbados? I was born there. Would love to go back!

    Back to the boat, I am still torn on whether to go with thre hulls of the PT06 floats (Front, Back and 11 x Mid section) or;
    4 Hulls of the PT01 (Front, Back and 7 x Mid Section) - It will likely come down to price! But both configurations come in just over 10 metres and have similar load capacities (7900Kg)
    What I dont know is how feasible it will be to shift a craft of that size and weight with outboards - I am hoping so.

    As for the toilet I am put of composting toilets as I fear the possible smell from keeping a box full of 'poop' in the bathroom. I am also not keen on having toilet that you cannot put toilet paper down. Even if it means buying a fancy toilet (as found on expensive Mega Yachts) I would rather make the investment as the experience for guests needs to be as close to a boutique hotel as possible so any compromises or inconveniences will impact their experience. Do such toilets exist for marine applications? I presume they would incorporate some sort of 'macerator' to chop the waste and paper up into small manageable chunks (forgive the mental word imagery, I couldn't think how else to put it). So what are my options?

    Back to the Engine, what do you think? Are twins necessary? I know they offer far better maneuverability
     
  7. Tom Peach
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    Tom Peach Junior Member


    I am in the process of working out the weight now, that is why I have only an approximation at this stage but I am designing in a lot of over engineering (i.e. 7900Kg load capacity) bearing in mind that it will likely come out heavier than expected and by the time you get 4/6 people onboard there is the best part of another tonne!

    I would not leave the guests the key to the engine and would likely wire in a 'hidden' disabler switch just in case they decide to get "creative".

    Thanks for your comments on the floorplan, and yes, the sofa in the lounge (Salon) doubles as a sofabed so it can sleep 4. I have also done a very similar floorplan shifting the master cabin aft and doing away with the aft deck leaving room for a narrow 2nd bedroom with bunks for kids so that allows for a sleeping capacity of 6 Max.

    As for the live-aboard scenario, I am planning to keep the boat in either Portugal or Southern Spain so I don't anticipate any problems with live-aboard Regs - at least I hope not.

    I am basically trying to do something very similar to these guys but on a slightly larger, more luxurious scale - The Homeboat Company Albufeira, Albufeira, Portugal https://www.booking.com/hotel/pt/the-homeboat-company-albufeira.en-gb.html
     
  8. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

    Hi Tom,
    Yes, I am from Barbados, and living here again now - in a previous life I spent almost 20 years living in England.

    I was going to ask which marina (in the UK) you are thinking of having your Air BnB houseboat in - but I see you mention southern Spain or Portugal. Yes, the regulations re 'liveaboards' there should be less onerous than in Britain (I am sure that there are many liveaboards in marinas like Vilamoura) - and the climate is nicer!

    Re the Homeboat houseboats in your link - I see a helm station on the foredeck. Are the guests allowed to drive these boats, or are they kept securely in their berths, only moving to go to the pump out station?

    Re super yacht loos, these are probably a bit OTT for you, but they give you a rough idea -
    https://extranet.evac.com/dl/005140?preview=true&revision=3.3

    An electric vacuum flush loo would certainly be nicer for your guests than the typical Jabsco type of marine loo which is usually found on sailing yachts and small power boats - you have to pump these by hand.
    Manual Toilets / Toilets / Marine Toilets / Marine / Xylem JabscoShop - Jabsco & Rule Pumps and more - from the experts http://www.jabscoshop.com/marine/marine-toilets/toilets/manual-toilets/

    It is perhaps telling that Jabsco only manufacture two types of manual loo, but have 32 different models in their electric loo range -
    Electric Toilets / Toilets / Marine Toilets / Marine / Xylem JabscoShop - Jabsco & Rule Pumps and more - from the experts http://www.jabscoshop.com/marine/marine-toilets/toilets/electric-toilets/

    Re the merits of having twin engines for manoeuvreability, at much increased cost, versus a single engine, you could perhaps have a single engine but also have a small inflatable dinghy with perhaps a 4 hp O/B motor that can be used as a 'pusher tug' to help manoeuvre the house boat?
     
    Last edited: Oct 1, 2020
  9. fallguy
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    fallguy Senior Member

    I paid quite a bit for Yamaha ycop ignition. The boat can't be started without a fob. There is an emergency procedure that will deliver 2500rpm max.
     
  10. gonzo
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    gonzo Senior Member

    I believe this would be considered a commercial vessel in the UK. Check all the regulations first, since the design and construction will be restricted by them. Also, there will be stability and flooding tests needed.
     
  11. missinginaction
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    missinginaction Senior Member

    Regarding the engine(s). I'll post a photo of my boat below. I use a T9.9 Yamaha high thrust alone and in tandem with my main V8 v-drive power plant. The boat is 26' LOA, 10.5' beam and weighs in at 7,000 pounds. So we're looking at about 8 meters by a little over 3 meters and 3,200 kg in the civilized world.

    At displacement speed and for maneuvering in tight quarters those high thrust outboards are in a word, fantastic. It sounds like your houseboat will be generally stationary and in sheltered waters. In your case a high thrust will be ideal. I can tell you that when you open the throttle on a high thrust hang on because you go, right now.

    I equipped my T 9.9 with a Garmin TR-1 autopilot (yes there is an autopilot option available for these engines). The T 9.9 will push me along all day at displacement speeds. I can fire the main engine and take the boat up to say 7 or 8 knots, a nice easy semi displacement speed. I set the T 9.9 at about 2,000 to 2,500 RPM and engage the autopilot. With the boats main rudder in the neutral position the T 9.9 will steer her all day long on a set course. I've been across Lake Ontario, an inland sea, in maybe 10 to 15 knots of crosswind and wave heights of 1/3 to as much as 2 meters. One and the occasional two meter seas on the beam makes me a little queezy after a few hours but the boat ran perfectly and the Yamaha held the course with no difficulty.

    Do an in depth analysis on your own or hire a naval architect. I'd think you could get some sound advise for not a lot of money.

    I'd estimate, based on my experience that a couple of T 9.9's or a single T 25 would be more than enough. I'd lean towards the single engine. You probably know you can go up to 60 horsepower but I don't think that would be necessary. Yamaha reliability is legendary. I've a 13 year old Yamaha motorcycle that still has it's original gel cell battery. My outboard has never failed to deliver. Make sure the shaft length is correct for your application and I'd suggest power tilt and electric start. You'll only buy this engine once.

    Pearl Aft.jpg

    Good Luck,

    MIA
     
    Last edited: Oct 2, 2020
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  12. Tom Peach
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    Tom Peach Junior Member

    You may well be right, however the plan is to build and moor the boat in Portugal or the Costa Del Sol, where I don't anticipate any problems
     
  13. Tom Peach
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    Tom Peach Junior Member

    Thanks for sharing your experience.

    I presume though that a houseboat on pontoon floats is considered far less aerodynamic, oh wait, I wonder if hydrodynamic is perhaps the correct term?? Anyway my point is the pontoon hulls will not moved through the water as efficiently as a planing hull found on a normal boat? That plus the weight (expected around 5000Kg) will surely need something beefier than a single High Thrust, although having looked at the price of some of these outboards (I reckon I can build the whole boat for less than the cost of the engine) I am thinking a single engine is an attractive option given how infrequently the boat will move! And how far too.

    My first Motorbike was a Yamaha and I loved it dearly. I was having a look at the Yamaha site and I like the controls and guages that go with the Yam's
     
  14. fallguy
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    fallguy Senior Member

    Might I ask, why the love for toons? Wouldn't a barge bottom offer more displacement for same cost?

    I never understand why anyone would want to build on less than ideal.

    Toons offer less drag for vessels underway. This one is planned to love nearly zero.

    Unless there is an unknown economic benefit, by the time you link them all together; a barge might be cheaper and easier to build upon.
     

  15. bajansailor
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    bajansailor Marine Surveyor

    Fall guy makes a good point above re the pontoons - what would be the cost (approximately) of 36 x PT06 floats?

    On top of that you will also have the steel (or aluminium - more expensive) structure to connect them together, and to sit the house on.

    It might be easier / cheaper in the long run to build a simple box shaped barge, with the bow end raked at say 45 degrees.

    Another advantage of a barge is that you can have all your tank spaces within the hull - with pontoons, the tanks would have to be arranged within the support structure for the house, or in the house itself.
     
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