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Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
edited November 2014 in Engine Discussions

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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    Do you have fuel flow monitors? They give you the best rpm/gph method for plotting out effiency.

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Dream_InnDream_Inn Member, Moderator Posts: 7,663 mod
    MT,I can usually go around 8-10mph with any boat I've been on and not only is the fuel rate decent but the bow stays down in the displacement mode pretty well.  As far as RPM, I believe it is no more than the 2k, probably a tad less.  As far as the wake, that is different of course from boat to boat.  I tend to start leaving a decent one at 10mph, but that is pushing 11 ton around.  Not sure if that helps.

    Dream 'Inn III -- 2008 400 Express

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Dream_InnDream_Inn Member, Moderator Posts: 7,663 mod
    MT, that's a smart Admiral! :-c

    Dream 'Inn III -- 2008 400 Express

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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    MT: if you take a bit of time and plot your gph vs rpm. And then over lay a plot of mph vs rpm you will see how fuel burn varies (it is not linear) for 'optimum' fuel usage. You see these on boat tests sometimes. In short, she's right. :D

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    Admiral wins -  I'll be doing the dishes (again) tonight. Thanks for the advice D.I. and B.D. most appreciated! I have a FOLLOW-Up question. My friend Pete D. (he's a marina mate with forum member Old Dog New Trix) has a Rinker EC 310 too - 350 Mags B3. He "displacement cruises at about 1200`rpm or so. He told me he likes to cruise with his trim tabs fully down as he feels it reduces "steering wander". He wanted to know if that was okay. I am inclined to tell him that it is fine. He "might" lose a bit of gas mileage, but tabs down at low  "displacement "rpm should be fine. Am I steering (pun intended) him right? MT
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  • Black_DiamondBlack_Diamond Member Posts: 5,439 ✭✭✭✭✭
    I know on my 342 1200 rpm is a fast idle and has me on the edge of no wake. I doubt tabs hurt gph much at those rpm.

    Past owner of a 2003 342FV
    PC BYC, Holland, MI
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  • Lifes GoodLifes Good Member Posts: 465 ✭✭✭
    Michael, here is another look at your question. I have twin 5.0. at 1000 rpm = 5 knots = 1.75 mpg.
    1900 rpm = 10 knots =1.5 mpg.
    2100 rpm = 12 knots = 1.0 mpg.

    so at that point I either stay back or throttle up to cruising speed. 3900rpm = 30 knots = 1.1 +/-

    hope that helps.
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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • MalloyMalloy Member Posts: 42 ✭✭
    Michael T I also have a 310 EC with twin 350 mag B3. I do not have a fuel flow meter. I would be very interested in your findings of RPM vs speed vs MPG at both idle and optimal cruising speeds. I have feel like I have high RPMs at cruising speed. Around 4000-4500 at 28 knots.
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  • TikiHut2TikiHut2 Member Posts: 1,431 ✭✭✭✭✭
    edited July 2013
    And for some other technical insight here's a contribution about your censored word that I learned from Raybo: The word "hard" cannot be followed by "on"......just sayin'    :D And now you know more than you'll probably ever need..... :-B
    2004 FV270, 300hp 5.7 350mag MPI Merc 305hrs, 2:20 Bravo3 OD w.22p props, 12v Lenco tabs, Kohler 5kw genset, A/C, etc.etc...
    Regular weekender, Trailer stored indoors, M/V TikiHut, Sarasota, Fl
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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • MarkBMarkB Member Posts: 3,976 ✭✭✭✭✭
    Michael T said:
    P.s. I got four **** in the above post for the word "hard" on the engines - is that a bad word on this site? I guess I better not say Viagra!!!! MT
    Looks like viagra got passed the editor. Will not use "hard" ever again, though.

    Boat Name: King Kong

    "Boat + Water = Fun"

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  • MarkBMarkB Member Posts: 3,976 ✭✭✭✭✭
    I have a single MAG 350 on my 260 EC. I need around 3600 rpm to get onto plane. After that speed quickly climbs to 25 or 30 mph.

    Boat Name: King Kong

    "Boat + Water = Fun"

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    edited November 2014

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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
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  • MarkBMarkB Member Posts: 3,976 ✭✭✭✭✭
    Not sure if it helps but my props via Bravo 3 drive are 20P.

    Boat Name: King Kong

    "Boat + Water = Fun"

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  • MalloyMalloy Member Posts: 42 ✭✭
    Michael T.

    Great info. I will have to check my set up next time I am out. I an stay on plane at lower rpm. I am new to owning a cruiser so I am feeling my way through a lot. I read in a review that the best gpm was at 28 knots. I thought that sounded high but that is why I have been cruising around that speed which is effecting my rpm.
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  • OldDogNewTrixOldDogNewTrix Member Posts: 166 ✭✭✭
    MT, I use the distance to empty to gage my best cruising speeds. I have the same engines, drives,etc... But a slightly larger boat. I find the best mileage is at about 1200-1400 rpm's. it drops off slightly at 1600 and 1800 is the maximum. After that, not only does the mileage drop off drastically, the actual speed is less at 2400 rpm than at 1800. On start up I have the Vesselview on the first screen to ensure all engine components warmup and are functioning properly. Then I toggle over one screen. I have never really encountered steering wander as Peter has but then again, I usually get lazy, put the auto heading on and just use the the arrows or joystick to correct positioning and turn as necessary.
    Wayne '09 340 EC
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  • brianluckbrianluck Member Posts: 174 ✭✭✭
    great information gentleman! 
    1994 300fv "General Madness"
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  • MarkBMarkB Member Posts: 3,976 ✭✭✭✭✭
    1200-1400 rpms?? I can hardly create a wake at that low of a speed.

    Boat Name: King Kong

    "Boat + Water = Fun"

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  • Dream_InnDream_Inn Member, Moderator Posts: 7,663 mod
    Just to follow up, I did a little slow cruising the past weekend.  1800rpm gave me 10-12mph. I burned best at 1600-1700 rpm (8-10mph) gave me 1.7gph.  (wish I could get that on plane!)

    Dream 'Inn III -- 2008 400 Express

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  • brianluckbrianluck Member Posts: 174 ✭✭✭
    what kind of distances are you covering with displacement cruising? 
    1994 300fv "General Madness"
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  • Michael TMichael T Member Posts: 7,227 ✭✭✭✭✭
    ODNT. Thanks for the info. Doesn't your vesselview give you a "real time"display of either gallons or liters per hour? MT
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