Cummins Marine Diesel Repower Specialists › Forums › Boats & Repowers

  • This forum has 86 topics, 323 replies, and was last updated 1 week ago by Sean.
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    • Cummins Marine Forum Topics
    • Repower 34' Libby with Cummins QSB 5.9 480

      This topic has 2 replies, has 2 voices, and was last updated byJohn Albaum 6 years ago

      June 14, 2017 at 9:14 am 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. Th…

      Started by: John Albaum

      2 Replies
      June 14, 2017 at 10:08 pm 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 Cu…

      Last Post by: John Albaum posted: 6 years ago

    • Prop Sizing Question

      This topic has 1 reply, has 2 voices, and was last updated byTony Athens 6 years ago

      May 31, 2017 at 8:56 am Prop sizing. question. These are 6BTA- 300 in a 34′ Hatteras Convertible. 12.5 beam – 26000 lbs loaded (No Trim tabs) ZF220A 1:5-1 gears. 3100 rpm NO LOAD – Current props: 4Blade Nibral – 20 X 19.5 X 1.5 WOT= 2675 RPM – NO BLACK SMOKE UNTIL IT GETS JUST OVER THE 2600 MARK, 2675 WAS ALL SHE HAD TO GIVE. Looking to get 2950rpm. NOTE**Started with props 20 X 21 X1.5 that gave me a WOT of 2600 RPM. The 20 X21 set up…

      Started by: paul j

      1 Reply
      June 2, 2017 at 7:24 am Paul, These are early 300B’s and they like to spin up easy to well OVER 2900 RPM when your vessel is loaded up as you use it–Typically I say “loaded for bear”…. Basically, you cannot under prop this engine as long as you are happy with the vessel speed at cruise RPM’s in the 2300-2500 RPM range.. Tell your prop guy this—————-Reduce my pitch/diameter/Cup or ??, until the engine …

      Last Post by: Tony Athens posted: 6 years ago

    • Cutlass bearing

      This topic has 1 reply, has 2 voices, and was last updated byTony Athens 6 years ago

      April 30, 2017 at 4:11 pm just hat my shaft shortened because when I repowered I had to slide the engine back I needed to replace cutlass so everything was out good time to do it now it’s all back together my question is new cutlass bearing should I be able to lift on the shaft and get any movementĀ 

      Started by: Derek chandler

      1 Reply
      May 9, 2017 at 8:00 pm All cutless type bearings are “sloppy” as to a shaft fit , Ā Maybe a Ā new 1.5″ cutless is .010-015″ over… If the Bearing is in perfect alignment with the shaft going thru it, yes you can always feel some lift.. As that alignment gets skewed, than is gets less and less.. Another issue is the ID of the strut as to concentricity–Many struts have out of round bores and will crush the bearing as it’s pressed i…

      Last Post by: Tony Athens posted: 6 years ago

    • QSC 540 or C9 565

      This topic has 8 replies, has 3 voices, and was last updated byBryan 7 years ago

      December 2, 2016 at 4:29 pm So what would be peoples thoughts?Ā  The QSC’s have 4000 hours and the C9’s have 2000 hours. It would beĀ  prop application for around 700 hours a year, both would be propped down to 500hpĀ  and driven for the best part at around 1800Ā  rpm. Discounting the general conditionĀ  of the engines would one be seen as the better choice? I had a water ingress incident and have 2 wet 3208’s and it seems the right time to upgrade. I understa…

      Started by: Luke Nelson

      8 Replies
      January 12, 2017 at 5:22 pm <p>Well the early pumps had issues that was recognized by caterpillar in a service letter. I’ve seen heui pumps last for upwards of 6000 hours and others 1500 hours was all the time they lasted this is where strict oil changes and regular maintenance ( anodes etc.) come into play, most times the pump can not make full pressure and the engine runs poorly at higher rpm. The downfall is when the pump fails and contaminates the oil rail …

      Last Post by: Bryan posted: 7 years ago

    • Repowering a 36 Northern Bay with a QSM 11/670

      This topic has 1 reply, has 2 voices, and was last updated byJerry Farnham 7 years ago

      November 27, 2016 at 4:57 am As started elsewhere this is the summary of a repower of my 36′ Northern Bay Downeast boat from a damaged QSM 11/670 to a reman QSM/670 . Ā  What seemed to at first be a simple plug and play turned into a seemingly endless series of one by one steps. Ā What was expected to be a 2 week out and in process turned into an almost 2 month affair.   Basics – Skipjack is a 36′ Northern Bay – classic Maine downeast hull. Ā Fully…

      Started by: Larry Backman

      1 Reply
      November 27, 2016 at 12:37 pm What/where is the old QSM11? Looks good. The yard should have caught the difference in couplings.

      Last Post by: Jerry Farnham posted: 7 years ago

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