Repowering

Discussion in 'Powerboats' started by Corpus Skipper, Jan 11, 2004.

  1. Corpus Skipper
    Joined: Oct 2003
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    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    O.K., I know this is a tall order, and open to lots of interpretation, but here goes. I've got a 26' Chris Craft flybridge "sport fisherman", a 262 Corinthian to be exact, 10' beam, not much deadrise(photos in my gallery). She has twin Crusader 350 c.i. 270 h.p. engines, 1.91:1 Velvet Drives, 1-1/4 shafts swinging 17x16 3blade props. She carries 135 gallons of fuel in 2 saddle tanks. She carries a 'glass radar arch and a bimini, but some day I'd like to replace that with an aluminum half tower. She'll do 27 knots at 5200 RPM (I know, underpropped) and cruise at 20 knots at 3200 RPM. She burns 24 GPH at cruise speed giving her a lousy 100 mile useable range (leaving 15 gallon reserve, avoiding pucker factor :D ). (speed/gph provided by GPS/Flowscan) I'd like to repower her, realistically with new Crusader 5.0 MPI 260 (?) hp engines, but don't know if the increased efficiency of EFI will extend my range as far as I want. (I'd like to double my range without adding tankage). The other option is diesel of course, but I'm a po' boy, and can't afford new diesels at $18000 a pop, and this boat isn't exactly a hot item on the resale market, so the expense would never be even partially recovered, not that I plan on selling. This boat soesn't like to go fast offshore, and I generally run 12-18 knots to avoid pounding. I've tried to calculate the h.p. I'd need in a diesel engine, gear ratio, etc., but I can't find much to help me out. I'd like to find a pair of used 4 cylinder diesels, and retain my trannies and shafts if at all possible. I don't need to go fast, but what I don't know is if my boat will run at the speed I want to run at efficiently. In calm water, she planes at 12-13 knots, but running this speed offshore leaves her dragging her tail and me getting .5 MPG. Not Good. Will 4 cyl. diesels run me at 12-16 knots efficiently without straining, through my current drivetrain? I know I'd have to re-prop. I don't mind dragging tail, smooths out the ride, but I know this is the most inefficient speed for my hull. Or the worst option, slap a for sale sign on her and get another boat (which I don't want to do, I like my boat! :( ). Any help will be appreciated.
     
  2. Corpus Skipper
    Joined: Oct 2003
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    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    OOPS! Forgot to mention, she weighs in at about 10,500 fully loaded with fuel, bait, ice, junk, beer, and fishermen! :D
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Repropping will increase your fuel economy. If the engine revs as high as 5200, it is wasting fuel. It increases 7 Knots with 2000 RPM increase. There can be several reasons. For example, the propeller blade surface is not enough and cavitates. The pitch could be too low. Of course, it is often a combination of causes. The best solution should be to increase diameter. How much clearance do you have?
     
  4. Corpus Skipper
    Joined: Oct 2003
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    Corpus Skipper Hopeless Boataholic

    Hey Gonzo,

    I have about 4 inches clearance from blade tip to hull. I believe by talking to several Bertram 28 ownersthat I should be able to cruise 20 knots at 2800 RPM or so. They do it, and they have deep v and outweigh me by 3000 pounds.
     
  5. Suede
    Joined: Dec 2003
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    Location: Sweden

    Suede Junior Member

    Hi Corpus,

    have an article here of a engine swap on a 25 sportfisherma fly, from 2xmarine power 165 to one yanmar 250. it's with follow up's on and new tests comparing against the old setup. the language wouldn't make any sence to you but if ya really interested I can give a few days to translate most of it...just give me a note...
    regards
    Olle
     
  6. Corpus Skipper
    Joined: Oct 2003
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    Corpus Skipper Hopeless Boataholic

    I'd reall like to see that! Thanks.
     
  7. Suede
    Joined: Dec 2003
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    Suede Junior Member

    Ok Craig,
    you'll have it before saturday
    keep in touch

    rgds
    Olle
     
  8. Corpus Skipper
    Joined: Oct 2003
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    Corpus Skipper Hopeless Boataholic

    Much appreciated Olle :D
     
  9. Carteret
    Joined: Jan 2004
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    Location: Eastern NC

    Carteret Senior Member

    Take a look at the GM 6.5's

    Hello!

    I' m new here and would like to add my 2 cents if that's OK.
    I am currently running a 26' John Allmand flybridge with a turboed 6.5 rated at 230 HP with 400 ft. lbs of torque and am very pleased. This engine is rated at 3600 rpm but I never take it over 2800. At 2600 rpm I am making 20 knots while burning only 4 gallons an hour. With your shafts and wheels and reduction gears these engines would be a great fit.
     
  10. Corpus Skipper
    Joined: Oct 2003
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    Location: Corpus Christi TX

    Corpus Skipper Hopeless Boataholic

    Thanks for the reply Carteret, who has these engines, and at what cost? I've heard the 6.5s in the trucks have had injector pump problems. I assume they're the same? You seem happy with yours. A friend had a 26 Allmand express with a 4B Cummins 135 HP single, slow but very efficient. I believe the weights of our boats are very similar, if the price is right, you've given me something to look in to.
     
  11. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Do you know who marinizes the 6.5's?
     
  12. Willallison
    Joined: Oct 2001
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    Location: Australia

    Willallison Senior Member

    1st up, welcome Carteret.
    4 gph sounds extraordinarily economical - you're getting 5 nmpg! Most diesels seem to consume around 20 hp/gallon/hour. Even @ 30 you'd only be using 120hp. Not doubting your word - just surprised that all....
     
  13. Carteret
    Joined: Jan 2004
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    Location: Eastern NC

    Carteret Senior Member

    6.5 Gm

    Hey guys thanks for the welcome,
    I don't blame yall for doubting, I couldn't believe it either. This engine is a smaller version of the GM 8.2 and it's nickname is the "Fuel Pincher". Both Penisular and Marine Power marinize these engines. The trucks did have injector pump problems but that was the electronic PMD. The Stanadyne DB2 mechanical injector pump is reliable and very price friendly. Corpus, I believe you should call Marine Power and price a set of 230 Sea Wolfs without the gears and reinstall the 1.91 velvet drives you are using now.
     
  14. zack
    Joined: May 2004
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    Location: Florida

    zack Junior Member

    John Allmand

    Cateret,

    I have the same boat 1977 currently powered by a single 350 crusader (270 HP), 1:1 BW swinging a 13" prop. I am looking to repower, and as you are well aware due to the size constraints choices of engines, gears, and prop diameters are limited. I am very interested in your configuration. Can you please tell me what gear (make and ratio), prop diameter, pitch, and number of blades, and year and model of the engine. This sounds like the way I want go with this vessel. Thanks in advance for your help!

    Zack
     

  15. Carteret
    Joined: Jan 2004
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    Location: Eastern NC

    Carteret Senior Member

    Repower with 6.5/6.2

    Zack,

    Sounds like you and I have the same vessel. Mine is a 76. I'm running a Marine Power 230 hp Sea Wolf. I bought the engine used and installed my existing BW 1:1 Velvet drive using the same mounts. I kept the 1" shaft and strut and went with a 14"d x 14"p wheel and am very pleased with the speed and economy. I did have to cut out my cockpit floor and raise the engine deck to allow for some height restraints. I lowered the rear cockpit floor at the same time because I never liked my knees being higher than the combing.
    If you would send me your e-mail address I would be glad to send you some pictures. The 6.5 with gear weighs in at 1,000 lbs. wet. I did have to raise the water line 1". Right now @500 hrs. and no problems. I like the safety, economy, and dependability of the diesel.The 6.5 got a bad reputation from the electronic injection pump. The marine version uses a Stanadyne DB2 mechanical pump. Very dependable. These engines are good replacements for recreational use. For comercial use I would reccomend Caterpillar, Detroit, or Cummins
     
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