Repower and Repurpose 23'

Discussion in 'Diesel Engines' started by crowsridge, May 2, 2010.

  1. crowsridge
    Joined: Apr 2010
    Posts: 141
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    Location: Eugene, Oregon

    crowsridge Senior Member

    Hello all,

    I am rebuilding a 23' Unflight that had been stripped to the hull. It had a 350 Chevy gas inboard and an 8' beam.

    The cabin and all have been removed and will be replaced with a CC or better yet, a pilot house very similar to a Shamrock PH, so will have 11' of fishing room behind. not counting the doghouse.

    I had played with the idea of an offshore bracket and an outboard, but have abandoned that idea. 15-18K? I want to stay inboard and go diesel.

    I am intrigued by the CDK project and have looked into twin VW turbo diesel 140hp.

    I found a pair of running Ford Lehman 6 cyl. diesels with Velvet drive 1-1. They are appx 100hp. A local boat builder told me I wanted a 115-150hp outboard.

    Questions

    #1 Ive been told diesel torque will get a boat up on plane much faster than gas and be a better ride. Opinions?

    #2 Is anyone familiar with that engine? How does the size compare to the 350? Room for two pass between or squeeze together and pass at the rail?

    #3 Would one do and save the other for a spare?

    #4 Would a single 6.9 be better?

    Thanks, Chris
     
  2. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    Chris,
    Lehman is/may be a bit heavy for that boat. It's 380 cu in. 1500lbs. I worked for Uniflite in the early 70s (engineering). Heard nothing but good things about the 23' Salty Pup. You may want/need a larger wheel for the diesel and that could give you some challenge as a helmsman. When you put it in reverse the stern may go as much to stbd as aft. Small twin turbo Yanmars may be better but brobably not cheap. Again expensive but a geared up drive for single eng twin screws would be very good (and expensive) too. Could the VW engines be inexpensive? That may be a good way to go. Somebody from France is on another thread talking about VWs ..go find.

    Easy Rider
     
  3. crowsridge
    Joined: Apr 2010
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    Location: Eugene, Oregon

    crowsridge Senior Member

    Thanks ER,

    I have found a few pairs of VW's. Im getting conflicting info though. Ive read 90hp-140hp for the turbo. A guy that has a VW shop told me today that theyre only 65-90. So with twins at 180hp? It came with 225. Im worried that it will be a slug. Im not at a point to buy new diesels. I would just buy a new 21' aluminum boat already to fish for that kind of money.

    The reason I wanted to do this is; to see if I can make it work and spend as little as possible until I know it works. If the salty pu turns out as cool as I envision it, I would drop new diesels in it and be fat and happy. Not there yet. Well? I am fat and happy! But you knw what I mean............haha
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    Check the hull for blistering. It is a common problem with those boats. I have senn blisters 10" in diameter.
     
  5. crowsridge
    Joined: Apr 2010
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    Location: Eugene, Oregon

    crowsridge Senior Member

    Its a 1964. The blisters started in the early 70's when they changed resins IIRC. This one is pretty good.
     
  6. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    They are great running boats.
     
  7. crowsridge
    Joined: Apr 2010
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    Location: Eugene, Oregon

    crowsridge Senior Member

    It has cool lines. Especially with the cabin removed. Sleek and alot lower sides that some of the boats I looked at like the Stripers that long. CC would look sleeker, but Im holding onto the PH to get out of the weather. And I want to figure out the power thing.

    There is a 6.9 liter powerstoke down the road that I could put in and be fishing by the end of summer. Them just get a kicker for trolling and backup. A quicker fix. A 6.5 diesel would go right back in place of the 350 gas that it had originally.

    So many quesrions......
     
  8. crowsridge
    Joined: Apr 2010
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    Location: Eugene, Oregon

    crowsridge Senior Member

    Now I am really confused. I read above where a guy is doing 24K with twin 115hp in a 32' boat??? My 23' only did 18K with a 225hp gas when new.

    How does torque play into speed? Do I need as much hp with the diesel as gas? I thought torque would just allo a bigger prop for bigger bite?

    I had a 19' Appollo with a 4 cyl. Volvo I/O I could carry three people and pull me up on two skis. It was fast enough for me. Id be happy to match that in diesel.
     
  9. Easy Rider
    Joined: Oct 2009
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    Location: NW Washington State USA

    Easy Rider Senior Member

    Hey Crow,
    HP is HP and that will tell you how fast you will go but you must have enough torque to get up to speed. Diesel HP, gas HP, 1929 HP .. all the same. And at WOT the gas and diesel engine will consume almost the same amount of fuel but at half load the diesel will consume far less. The guy w the 32' w twin 115s probably had a light boat. Uniflite's are not light. A pair of 80s or 90s would probably work for you but 2 115s seem like a sure bet. The two 140hp VWs will probably be good too but keep in mind that what I offer here is strictly opinion.

    Easy
     
  10. crowsridge
    Joined: Apr 2010
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    Location: Eugene, Oregon

    crowsridge Senior Member

    ER, I love opinions!

    Been racking my brain on repowering. I found a 6.5 yesterday a guy was selling. But its only 180hp. I just dont think I will be happy with that. The boat came with 225 and would only do 18 knots.

    Today I looked at a nice 97' 7.3 ltr turbo diesel with 275hp stock. It had a manual transmission, so I wont have to mess with the computer issues either. I found several heat exchangers that would be remote mounted. Now, I need to design where the waste water dumps into the exhaust on its way out the stern. Somewhere I read that diesel exhaust is cooler than gas? Need to research that more.

    Have to go find a thread on sizing the new shaft and prop now too.


    Thanks, Chris
     
  11. kapnD
    Joined: Jan 2003
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    Location: hawaii, usa

    kapnD Senior Member

    How much will you really use the boat?
    If its not a daily runner, you will probably be money ahead to stay with the gasser.
    Equal or greater horsepower in diesel will cost lots of dollars and add many pounds.
    Marinizing a truck motor is a expensive and not always satisfactory option, better to buy a rebuildable marine engine that comes with all the bolt-ons already in place.
    Do some reading on Boatdiesel.com, lots of great info there.
     

  12. crowsridge
    Joined: Apr 2010
    Posts: 141
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    Location: Eugene, Oregon

    crowsridge Senior Member

    Thanks KD

    This wont be a daily runner until I retire. It is more of a personal challenge.

    The modifications I need to make are generic. Its just an open hull. designing the engine compartment, exhaust, fuel tanks and remote heat exchanger will be similar whether gas or diesel. I would need a third battery, but wont need marine sealed electrical parts. So I save there.

    The boat came with 225hp and the one I picked has 275hp and is 225lbs heavier. I lost all the drag and weight of the cabin etc. so I don't think that will be that much of an issue.

    If I had an expensive boat, you are absolutely right go full blown Yanmar marine etc. But I have a $500 boat and trailer. The motor is $2100, fuel tanks $300. $2000+/- marine plywood and glass/resin. The paint, hardware and misc. will add up too. But lets say my original budget of $7000 goes very wrong and I double it. Where could I get a basically new 23' diesel drive , 275hp. center console custom built fishing machine for $14K?

    Personal satisfaction? Priceless!

    All the input (and pictures) would be great!

    Thanks, Chris
     
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