Lightweight Turbo Diesel Jet setup

Discussion in 'Jet Drives' started by groper, Jan 21, 2014.

  1. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,164
    Likes: 961, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    It's going to be dictated by the availability of funds as well ! Dunno about cheap marinized diesels, seems unlikely to me. If I'm wrong about that, I'll have what he is having ! In any event, the whole idea would substantially up the weight of a vessel that has been on a strict weight control regime since day one.
     
  2. groper
    Joined: Jun 2011
    Posts: 2,467
    Likes: 123, Points: 73, Legacy Rep: 693
    Location: australia

    groper Senior Member

    I found several common rail 2.0L turbo diesel engines from 2010 model cars with 20,000km on the clock at auto salvage wrecking places across australia. The going price for a complete engine including turbo, ECU, starter motor, etc everything needed to get it running for $2500. This is very cheap compared to a new yanmar or similar at over $20k.

    The marinisation is not too difficult or expensive. The main challenge i see will be to edit the ECU so it doesnt get confused with not having a gearbox ECU to talk to or some of the other inputs it needs to see in order to run without tripping itself out and going into "limp" mode. The jet boat guys have marinized all sorts of common rail diesels, from VW`s to toyota prado`s to nissans, the list is endless.

    The real problem i found is sourcing the jets - brand new they are going to cost me over $10k each by the time ive imported them or bought locally made units. My pockets arent deep enough im afraid...
     
  3. johneck
    Joined: Nov 2011
    Posts: 247
    Likes: 14, Points: 18, Legacy Rep: 117
    Location: New England

    johneck Senior Member

    Sounds like you have stumbled over the three main reasons that outboards are the way to go for small boats. They are more efficient at any speed less than about 40 kts, cheaper due to simple drivetrain and components and easier to fit since they are not inside the hull.
     
  4. groper
    Joined: Jun 2011
    Posts: 2,467
    Likes: 123, Points: 73, Legacy Rep: 693
    Location: australia

    groper Senior Member

    I'm not convinced outboard motors are more efficient.

    The efficiency of a jet certainly improves with speed, however the efficiency can be comparable to a prop at much lower speeds than 40kts if the jet size and impeller is well matched to the engine and boat.

    A Diesel engine is more efficient than a petrol engine, and diesel fuel has a higher energy density than does gasoline.

    Outboard motors spin rather small propellers, which are inefficient in themselves unless very lightly loaded on little planing hulls...

    For me it's purely a cost problem, otherwise it would certainly have been feasible and allowed a shallow running condition and beach ability for its intended use.
     
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,164
    Likes: 961, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    I note those jet units are not that light, the time you fully marinize those diesels and mate them to a jet drive, your weights will have climbed well beyond outboard weights, at least twice as heavy imo, and then there is entrained water, and the way jets have to lift water, all of which is weighing your boat down, I don't know whether your boat is near large enough to warrant diesel/jet, the large reef cats are a different proposition altogether.
     
  6. masalai
    Joined: Oct 2007
    Posts: 6,823
    Likes: 121, Points: 0, Legacy Rep: 1882
    Location: cruising, Australia

    masalai masalai

  7. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 110, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    I understand the concept you are going for , but think life would be far simpler with a different choice.

    Diesels are more efficient than gas , perhaps, but the cost is huge complexity , electronic injection and one or two turbos .

    Used car takeouts that are light weight do not have the endurance of a normal boat diesel, think auto or outboard , 2000 hours surely not 20,000 as industrial engines get.

    The loss of efficiency at slower than optimum jet drive speeds would easily eat the few percent that diesel is cheaper to fuel than gas.

    Rethinking outboards , especially installed on a hyd lift jack plate could make shallow water running and beaching far easier.

    Shallow water eats props from abrasives , outboard props are cheaper than jet drive impellers.And lots easier to change.

    The vessels service use , hours per year could be plugged into a cost chart to see just what 5000 hours would cost, in initial costs , maint , service life and fuel cost.

    I think unless you are planning over 1,000 hours a year , a pair of quality OB would give the easiest and cheapest service life.

    Buy 3 , and it will give overnight repowering should that be needed, and sell each as 2000 hours is reached to a yacht guy.
     
  8. masalai
    Joined: Oct 2007
    Posts: 6,823
    Likes: 121, Points: 0, Legacy Rep: 1882
    Location: cruising, Australia

    masalai masalai

    Consideration of fuel sources, USA petroleum (gas) is 'subsidised' - WTI is holding at less than US$98/barrell in USA (not available anywhere else in the world. Australia, PNG prices for fuel relate to TAPIS from Singapore at US$115/barrel PLUS and the engines on Frosty's boat and my Kubota toys will both run on coconut oil in the tropics with a normal fuel temperature of 26deg Celsius in the tank and is renewable energy and 10% cheaper and less in main ports and cheaper in remoter regions... Small diesels for me... The USA oil and gas fields that are being fracked to recover are costing more to produce than the selling price... Think carefully of the fuel source....
     

  9. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 110, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The USA oil and gas fields that are being fracked to recover are costing more to produce than the selling price... Think carefully of the fuel source....
    __________________

    Nonsense , the co. doing fracking are awash in profits much to the chagrin of the current administration that dumps billions into failed solar campaign contributors.

    There is not one dime of subsidy to oil co , although the far left wants to count the cost of the entire US military as an oil subsidy.

    The reason there are 2 different prices world wide for oil is how easy or costly it is to refine into local required products.

    Sweet oil is enough cheaper to refine to Jet A gasoline and diesel than heavy crude with loads of sulphor to be removed, that it commands a higher price.

    Bunker for ships and large power stations is less refining , and usually goes to places that dont give a damn about air quality.
     
Loading...
Similar Threads
  1. Seabear23
    Replies:
    4
    Views:
    3,133
  2. weehenry
    Replies:
    1
    Views:
    3,010
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.