Gph

Discussion in 'Diesel Engines' started by girvin, May 28, 2010.

  1. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    ...no way a two stroke GM is going to be an economical cruising engine, you need low rpm, 4 stroke, long stroked engines.
    ...Gardner or the old Komatsu 24 litre are very economical. The Komatsu is used as the old Lugger.
     
  2. girvin
    Joined: Dec 2009
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    girvin Junior Member

    Your right Tad I was actually gonna call you when I find a boat since you are close. DO you do surveys? or for hire to help with ballasting and conversion wieght. I don't think ocean producer is gonna happen anyways I just need to sell my damn sailboat. I wish I could get fearless with a gardner that would b my dream choice. Thanks for all the help guys. I plan on documenting the build when time comes. Hopefully I can get off this rock and back to warm water. THe cold water is giving me aches to the point I have to choose my surf sessions.
     
  3. Guest62110524

    Guest62110524 Previous Member

    things have moved on since Gardner
    they now have things called common rail
    fuel used in ships grams kw/hr has come down and down and down, and yes they do as many hours as those big hunks of iron did, nothing can stand still
    Although I have built boats since mid 70,s I served my time diesel fitter and helped start the Newcastle branch Cummins In those days the 855m (cu onch) 6 inline was the best engine around, in those days it was far superior and more advanced that any Gardner was It still is the basis for todays engines Sure you HEAR abt Gardners, but its all legandI am afraid, yes lilike many English engines, Kelvin, Lister, lister blackstone, Ruston Gleniffer,were are much of a muchness great in the day But oh my God you try paying for a crankshaft trucks and quarry equipment are perhaps the biggest testing ground for diesels in the 300-- 1500 range, in trucks Foden, ERF from England used to use Gardners,, then along came Cummins
    modern metals, precise fitup have given the longlevity to lighter engines
    Last I heard Komatsu would not comply eu or us smoke emissions, so thats how inefficient they are
    nothing is romantic as a slow beating diesel But these days its all about running cost, and that takes into acoint lonlevity
     
  4. girvin
    Joined: Dec 2009
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    Location: Vancouver Island

    girvin Junior Member

    I like the old 12 valve with the P pump they cam in the 94-97 dodge 2500 pickups. I just don't want any electronics to have to depend on thats why I like the old mechanical injection.I am open to things what cummins do you suggest? I like them bc they are cheap to work on. I have some experience with the 12 valve but only with trucks. I have seen alot of them with 300k miles on them and still going. I just havn't seen any of the fishing boats up here getting 2 gph at 7.5 knts except the ones with gardners. I would rather have a cummins bc of the price and ease of parts. I feel like my sailboat will never sell and I won't get to start my next boat ever.
     
  5. Guest62110524

    Guest62110524 Previous Member

    well you are dead right abt Electronic control in many ways,
    If things go wrong, and often they do, then what do you do> I was in NZ recently working on a boat, new, with 310 volvo You hade to program the control the right way of you buggered the engi9ne management Whilst I was there the mans brother came round, said his employee had somehow shorted the pcb on a tractor and the board was 9000 dollars,
    So you mean the B series, 6bt , yes I know they do 20000 hrs which is a lot for a bored in the block engine
    to get wet liners you need C series
    Surely you can google second hand engines, there are some very big sites there
    what sort of sailing boat are you trying to sell
     
  6. girvin
    Joined: Dec 2009
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    girvin Junior Member

    I have a Wharram pahi 42http://www.sailingtexas.com/swharrampahi42100.html

    We have the volvo pent 330 in a couple of the whale watching boats. they are pieces of crap. Shattered 3 impeller shafts in 2 years and only got 1800 hours before the last one let go. what are wet liners? I will definetly try and take a service class if I get a cummins there are a few diesel schools out here that use cummins. And to think I had to take one of our boats through 27 ft waves and 35knt winds and trust that stupid volvo. I am glad its not winter here anymore LOL.
     
  7. Guest62110524

    Guest62110524 Previous Member

    Wet liners are like sleeves, but the sleeves do not come into contact with the block at the bottom end, they have o rings, usually 2 narrow and one wide and flat , at the top end they fit into the counterbore of the block
    The beneifit is, if you seize one pot, you replace one liner, one piston
    Whereas bored in the block , like cars, you stuff one piston you either ebore the block and fit oversize pistons , or you put in a new short bloc
    But I have never heard of a B doing either Thye are very good and I fit the 4b to my sailing yachts
    But now the 4b mech is no longer made
    so we have to change to JD 4, which is a fine wet linered engine
    googles used diesel engines, there are many running take outs
    Yes Volvos and yanmars, we say HAND GRENADE RATED
    Cummins underate their engines Others overate, that is they allow bigger shp for given operating cycles, just to sell engines The strategy does not work, long term that is
     
  8. girvin
    Joined: Dec 2009
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    girvin Junior Member

    Hand grenade Rated LOL that great. OK I know the wet liners just didn't know there name. So I should look for a c series if I end up with a cummins? Thanks for all the help woosh Tad and everyone.
     
  9. Guest62110524

    Guest62110524 Previous Member

    so we are getting back to this 5o footer>? a single diesel, yes c series, in late 80,s I put a C in a mussell boat(see my gallery I think it may be there), it has done 30000 hrs and just keeps going
    If you buy a twin screw 50 2, Bs 210shp, you can run on one
     
  10. Pierre R
    Joined: May 2007
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    Pierre R Senior Member

    The Detroit 8-71 is a two cycle engine and depending on whether it is tubocharged or not will deterimine its fuel burn at low power settings. Detroits do not like to run slow and are really set up to produce power at about 60% to 70% of rated power. At that setting the 8-71 will burn as low as 0.4 lbs of diesel per hp per hour. When you get down into the 20% range these engines reallys start to use fuel in comparison to a modern 4 cycle. At 20% you might expect 0.6 lb per hp. Lower yet the fuel burn gets even worse and you get some slobbering in the air boxes. The good thing about detroits is that they are cheap to rebuild, rugged and deliver a lot of hp per lb of engine. The down side is range of power and fuel burn.

    A newer common rail tier 2 diesel will burn as low as 0.335 lb per hp and really shine in comparison to the detroit at low power settings. They use far less fuel at low power settings because they don't drop off as drastically as a detroit.

    If you have a 50 ft boat burning 5.5 gph with a Detroit 8-71 the hp being consumed is around 75 hp. Assuming a naturally aspirated 8-71 that is somewheres around 25% power. Low already for the detroit.

    A 50' lwl at 8 knots at 75hp is probably around 63,000 lbs. This weight seems very reasonable for comfort in a passagemaker of that size. Now we drop that to 7 knots and we will probably be around 51 hp. But the good old Detroit is really dropping off so its burning around 4.4 gph. A John Deere common rail 6068 of 178 hp would be burning around 3.6 gph at 8 knots and 2.5 gph at 7 knots.

    Consider the 8 knots speed to be good for passagemaking with a 15%-20% reserve and the 7 knots speed needs around 25%.

    You do the math on range.

    Everything here is assuming you gave good information. The above also does not take a generator of heavy electrical usesage into consideration.
     
  11. girvin
    Joined: Dec 2009
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    girvin Junior Member

    Thanks pierre I messed up earlier it was a lugger. I got 2 boats confused.
     
  12. Pierre R
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    Pierre R Senior Member

    If a lugger is developing 5.5 gph at 8 knots then the boat is much heavier. Say in the neighborhood of 82,000 lbs.
     
  13. girvin
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    girvin Junior Member

    I am also wondering if that is full loaded it hauls like 30k pounds of crab. What would the lugger do at 7knts? I have to wait to see it with a broker before I can get some more info
     
  14. Pierre R
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    Pierre R Senior Member

    I have no idea. I gave you the approximate weight given 5.5gph on a Lugger at 8 knots with a 50' waterline.

    I do not know what size Lugger or anything else about the boat. I am just running it through the equations. All numbers are approximate and not written in stone.

    At 7 knots probably 3.7 gph.

    An old crab boat is not likely to be a really good hull design for conversion to a passagemaker You would likely be money ahead in the long run to start from scratch.

    82k is probably with a partial load of crab. You would need the boat in a heavy condition as well for sea comfort. Weight costs fuel. I would guess the waterplane is in the low 500 ft^2 so 82k lbs is probably going to result in a very deep draft restricting you in many locations.
     

  15. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The Detroit 8-71 is a two cycle engine and depending on whether it is tubocharged or not will deterimine its fuel burn at low power settings. Detroits do not like to run slow and are really set up to produce power at about 60% to 70% of rated power. At that setting the 8-71 will burn as low as 0.4 lbs of diesel per hp per hour. When you get down into the 20% range these engines reallys start to use fuel in comparison to a modern 4 cycle. At 20% you might expect 0.6 lb per hp. Lower yet the fuel burn gets even worse and you get some slobbering in the air boxes. The good thing about detroits is that they are cheap to rebuild, rugged and deliver a lot of hp per lb of engine. The down side is range of power and fuel burn.

    The above is correct 2 stroke thinking, and explains WHY DD createed 2-3-4-6-8-12-16 cylinder engines.

    Use 20 hp to max 30 hp per cylinder as a guide and the fuel burn will not be bad.

    Cost is a huge consideration , a used DD can cheaply be found , and any extra in fuel use will be no problem as used is maybe $3000, with tranny, and new for a similar 24/7 power rating is $20,000 to $30,000.

    That's a lot of diesel for most cruisers.

    FF
     
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