Cummins Marine Diesel Repower Specialists Forums Boats & Repowers Repower 34' Libby with Cummins QSB 5.9 480

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  • #19904

    John Albaum
    Participant
    Vessel Name: Wound Up
    Engines: 265hp Deere
    Location: Boothbay, Maine
    Country: USA

    I’m looking to repower my 34′ lobster boat(Libby 34×13). I have a Deere 6068SFM50 rated at 265hp with a ZF280 at 2:1 to a 2″ shaft spinning a 24×25 wheel at the moment. The engine I’m looking at is a very low hour QSB 5.9 at 480hp. I know the engine will fit and my gear and shaft will handle the horsepower. My questions revolve around the exhaust and the power steering pump that is already on the engine. The Deere has a 4″ exhaust outlet that goes to a 6″ exhaust before the engineroom bulkhead and is 6″ through to the stern. Is 6″ sufficient for the 480? I also have power steering run off a PTO on my gear, with 2 helm stations and an autopilot solenoid. Would the power steering pump on the 480 be compatible with my system so I could get rid of the PTO on my gear?

    Thanks
    John

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  • #19968

    John Albaum
    Participant
    Vessel Name: Wound Up
    Engines: 265hp Deere
    Location: Boothbay, Maine
    Country: USA

    Thanks for the reply. With the Deere I can make a little over 19kts at WOT and about 13.5gph, and that’s right were I would like to cruise, so I feel like that wouldn’t be too hard for the 480 to do. I’ve read they can cruise comfortably at 17ish gph. I’d be doing 300-400 hrs per year so not too much. I’ve attached a picture of the engine with the power steering pump attached. I don’t know if this is a Cummins add on or aftermarket, and was hoping it would be able to run the power steering I currently have. If not it would come off and I would just keep the PTO as is on my gear. As for the exhaust, the Deere exhausts to port and the Cummins is to starboard so I’ll have to have a sweeping mixer made up to feed into my port side tube. I’ll have to get measurements of the exhaust and muffler when I can get to the boat again.

    Thanks
    John

    #19919

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    QSB 5.9 480 PTO

    Per the Book,
    Cummins does not allow any PTO options to be used the the QSB5.9 480…….

    With that said, anything can be done.. It just comes done to what you want to accomplish, and then a combo as to how hand’s-on as to doing it yourself, vs. how much you can afford to have someone else engineer or build/provide what you need.

    Cummins PTO and other PTO Solutions

    PROPPING: Understand that if you want decent life and performance from this engine in a commercial application , for PROPPING PURPOSES, use a max of 460 BHP at 3500 RPM high cruise at 2700 or less..

    EXHAUST: the entire system needs to looked at with exact measurements, type & number of bends, type of water injection, etc etc before any meaninful comment could be made.

    Tony

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