Cummins Marine Diesel Repower Specialists › Forums › General Discussion › 38 Evans Repower

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  • April 6, 2022 at 1:56 pm #130123

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    Hello. Looking for some advice on a Repower of my 38 Evans.  The boat currently has a good run I g QSC 490 with a 286a 1.75:1 spinning a 26×23 dynaquad 4 blade.  The boat is heavy 28,000 pounds.  It is a passenger boat so hauls around some loads.  <br />  With no passengers she hits 90 percent load at wide open throttle.   Loaded with 8-10 passengers she is running 96ish percent load wide open throttle.  Cruise at 2200 is 14-15knots 67 percent load 17 gal a hr.

    Looking to get a 16-17 knot cruise, and could care less about wide open throttle.

     

    options qsl9 450 same gear turning a 28×24 prop according to prop calculator 

    qsm11 610  new gear with same ratio, but spinning same prop.

     

    so if the qsl9 and the qsm11 spin the same prop, but you can run the qsl9 all day at 1900, but can only cruise the qsm11 at 1900 of a 2300 rpm engine.  Wouldn’t both engines produce the same speed?    Any opinions out there??

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  • April 13, 2022 at 4:41 pm #130382

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

    If I needed to replace engines and started from scratch, in your application I’d go with a QSL9 450 set-up right.. But realistically, you need about 15-20% more more engine than that.. Cummins does not offer it. 

    April 10, 2022 at 3:43 am #130237

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    Thanks everyone for the info

    Tony if you were going to recommend a Cummins Product what would you recommend?   Keep in mind this is a 1,000-1500 hr a year boat.  Trying to maintain a 16-17 knot cruise, which yes the QsC will do, but that’s at a 2250 cruise.

     

     Thanks

    Kane

    April 9, 2022 at 8:36 am #130216

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

    To me it all comes down to how much fuel the owner is willing to burn to get 2 extra knots.. His numbers say that the vessel needs ever bit of 380-400 HP put into the prop  to do it.. That’s basically 20 GPH no matter how what engine you use as long as the vessel weight does not change……………….Both the QSC and QSL9 can do that, but the QSL will stand up much better  over the long run………………….    Maybe too much boat and not enough engine if this is  about the need for speed ? His current propping is right on–Just move to throttle hand a bit go get the speed but expect less engine life before you need a top end along with additional maintenance and nit-pick issues

    April 8, 2022 at 6:06 pm #130195

    Steve Lewis
    Participant
    Vessel Name: Just Us
    Engines: Cummins 480CE
    Location: Marblehead, OH
    Country: USA

    I am wondering if your current ZF Gear and the 2 inch shaft would be sufficient for the added load of the larger propeller………..

    Tony and team can provide that level of clarity.

     

    April 8, 2022 at 2:02 pm #130190

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    if I went that route which is what I was hoping for, I would like to keep my 2” shaft and 286a gear 1.75:1

    what was throwing me off was when I ran the prop calculators on the qsm11 610, and the qsl9 450 both engines could spin the same prop 28×24.  <br /> To me it sounds like I could cruise the qsl9 at 1900 or the qsm11 at 1900 and make the same speed.  I do have clearance for a 28” wheel

    April 8, 2022 at 1:04 pm #130186

    Steve Lewis
    Participant
    Vessel Name: Just Us
    Engines: Cummins 480CE
    Location: Marblehead, OH
    Country: USA

    KB,

    I have attached the performance report for the QSC490.  Based on my review of your posted numbers, you are about 1gph UNDER the 490 curve.  That is quite good.  What I am wondering is what is the diameter of the current prop shaft?  The reason I ask, and beg Tony’s forgiveness if I am overstepping, is that the QSL curve shows 17gph at 1900rpm(17gph is your cruise fuel burn rate at 2200 with the 490).  The QSL develops  almost 40% more power than the 490 at 1900rpm.  If you run up to 2100 then we are talking close to 47% more.  Can your current drive train handle that or are you looking at substantial modifications to get a QSL/QSM into your boat?  Tony, again forgive me but, I am interested in this thread as a number crunching engineer.

    Are those 2 knots worth the cost of the engine, trans, shaft and structural modifications? 

    April 8, 2022 at 5:07 am #130172

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    Here are the numbers with 12 passengers, and a ton of gear.

    1800 10 gal hr

    2100 15 gal hr

    2200 17.2 gal hr

    2300 19 gal hr

    2400 21 gal hr

    2560 wide open 24 gal hr

    At 2250 the boat feels like it likes that speed, but I feel that’s asking to much from the engine, that’s why I’m considering the repower.   Any suggestions??

    April 7, 2022 at 3:47 am #130138

    Kane Bounds
    Participant
    Vessel Name: Fish Bound
    Engines: QSB 5.9 355
    Location: Ocean city MD
    Country: United States

    The weather is going to let me run a trip tomorrow.  I’ll grab all the info.   Thanks for the response.   Looking for a little better performance then I have now.   Thanks 

    April 6, 2022 at 4:45 pm #130133

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

    QSC 490

    Post what I am asking below as load % is 100%  meaningless at this point,  or when trying to figure out your prop loading and things related the how the current engine set up in your vessel is actually loaded.

     

    GPH at 1800, 2100, 2200, 2300, 2400,  2500, rpm and WOT /with max rpm reached..

     

     

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