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Thread: RPM to GPH

  1. #1
    Member Alaska Gray's Avatar
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    Default RPM to GPH

    I a have a 26 hewes w/ twin yamaha 115 4 stroke.
    This weekend I ran it @ 53RPM and buring 12-13 GPH
    then when I went to 58RPM I burned 21 GPH
    does this sound about right? I'm just trying to make sure that I'm not burning more then what's normal.
    Living the Alaskan Dream
    Gary Keller
    Anchorage, AK

  2. #2
    Member Sierra Hotel's Avatar
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    Default

    AG, I've got the same setup. Last week out of Homer I ran 4700rpm and saw 12 gph, yielding 25 mph. 5200 rpm gives me 30 mph and 15 gph, and WOT shows me 6000 rpm, 21 gph and 36 mph. I'm just at the motor breakin period (10 hrs), so it might change a little - but I'd say my numbers are pretty darn close to yours . . .

    Were you at WOT at 5800?

    SH

  3. #3

    Default Single engine

    I run a single F115. I usually cruise no higher than 4400 RMP, and I'm consistently at 3.5-4 GPH. If I was running twins, I would assume that equates to 7-8 GPH on a different setup. I've never tried running it above 4500 for an extended period (don't need to), but I'd be curious to see what that does to my fuel economy.

  4. #4
    Member Alaska Gray's Avatar
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    Default

    I usally get between 58-59WOT

    I ran it will allot of gear and 5 of us and got up to 36MPH @ 58RPM
    Living the Alaskan Dream
    Gary Keller
    Anchorage, AK

  5. #5

    Default Gas

    Same set up. Sounds a little high but maybe not. FloScan fuel management gauges would be nice.

  6. #6

    Default Sounds pretty good

    to me. I have twin 150's and burn 32-34 gph at 5900 rpm and 44 mph.

  7. #7
    Member Sierra Hotel's Avatar
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    Quote Originally Posted by Sierra Hotel View Post
    AG, I've got the same setup. Last week out of Homer I ran 4700rpm and saw 12 gph, yielding 25 mph. 5200 rpm gives me 30 mph and 15 gph, and WOT shows me 6000 rpm, 21 gph and 36 mph. I'm just at the motor breakin period (10 hrs), so it might change a little - but I'd say my numbers are pretty darn close to yours . . .

    Were you at WOT at 5800?

    SH
    Update from this weekend's run out of Whittier


    4500 rpm 25 mph 11 gph
    4900 rpm 29.8 mph 12 gph
    5200 rpm 32 mph 13 gph
    5500 rpm 34 mph 16 gph
    6000 rpm 36 mph 20 gph

    For me it looks like 4900 rpm is the "sweet spot" for speed/fuel efficiency. Based on a 75 mile round trip, I actually burn less fuel at 4900 rpm (30 mph) than I would running at 4500 rpm and 25 mph.

    Guess I'll be keeping it right around 30 mph max. . . .

    SH

  8. #8
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    Default Here is average data on 150' with 19" Prop

    4whlr,

    I have same setup as you do, Are you using 17 prop.?
    Can you list your RPM vs Speed Data.

    Im using 19 prop and here is my data.

    RPM MPH GPH MPG
    1000 7 1.5 4.5
    2000 n/a n/a 2.0
    3000 n/a n/a 2.2
    3800 30 11.5 2.6
    4000 33 13.8 2.4
    5500 46 30.6 1.5

    These are average data from last season and few trips this year.

    Thanks

  9. #9

    Default

    With gas prices what they are I can see less trips this year with the big boats.

    8 hours run time on 3 gallons of gas with an average speed of 10 mph, I would like to increase the speed some but I will be happly fishing and floating as much as possible this year.

  10. #10
    Member Sierra Hotel's Avatar
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    Default

    Quote Originally Posted by alaskamokaiman View Post
    With gas prices what they are I can see less trips this year with the big boats.

    8 hours run time on 3 gallons of gas with an average speed of 10 mph, I would like to increase the speed some but I will be happly fishing and floating as much as possible this year.
    ROFL Alaskamokaiman! What about the four fishing buddies? Where do they sit?

    SH

  11. #11

    Default Yamaha 115 Gph

    My father in laws 25ft Wooldridge Deep Water with twin 115 Yam with a counter rotater and 18 pitch Yamaha stainless props uses 7 to 8.5 gph. He can cruse at 4100 rpm 29-30 mph in calm seas and get 7gph with 4 guys and gear for the weekend. The boat is 6500lbs wet with gear and food for a weekend.

    He just recently sold it and is having a new 27ft Pilot model built. FishHog on the forum has it now. He has had it down as far as 6.5gph at 4000 rpm with a light load.

  12. #12
    Member Queen of Kings's Avatar
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    Default Fuels Stats

    Just for infomration I just installed my new Flow Meter, Northstar F210,and here are the results for a 220 Sea Runner Soft Top Yamaha 115
    MPH RPM GPH
    19.5 4000 4.1
    25 4500 4.9
    29 5000 5.9
    33 5500 7.4

    MY WOT is normaly 5900 and 36 MPH, but iy wasn't quite smooth enought to go there. I certainly like the good GPM though with that 115.
    2003 220 Hewescraft Sea Runner 115 Yam'y, Soft Top "Schmidt Happens"

  13. #13
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    Default best value - flow meter

    I see there are some referencing the NorthStar meter and some with the FloScan. In doing some research it appears that one can spend anywhere from $150 up. What are your thoughts on value for the dollar. Realizing that anything is better than nothing. I am running twin 115's, 2 strokes, and have no idea what I'm burning. I just know that it's alot. I can easily burn 150 gallons in a weekend in PWS. So value for the dollar. Any thoughts?

  14. #14

    Default

    The floscans are a bit more, but most people that have them like them. If you are burning 150 gallons a weekend, any fuel meter should pay for itself fairly quickly. You can likely save burning a couple gallons an hour by using a flow meter to find your most efficient cruise speed. Think $6-$10 an hour saved.

  15. #15
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    Default Floscan and four strokes....

    I put a new Suzuki 225 on my boat, but Floscan's website scared me away from buying a meter. Are you guys having success with the GPH readings in conjuntion with any of the engines listed below? I hope so, I'd like to have the information for my boat.

    The following is copied and pasted from Floscan's website.

    - Evinrude E-Tec 2-cycle
    - Mercury Verado 4-cycle
    - Suzuki 4-cycle
    - Yamaha 4-cycle
    The engines listed above have two fuel pumps. Because the engine's lift, or low pressure pump cycles on and off while filling the vapor separation module, the FloScan instrument GPH/LPH readings will constantly fluctuate between 0 GPH/LPH and approximately 25-50 GPH or 95-190 LPH depending on lift pump and engine size. Though the GPH/LPH readings are unusable, the FloScan instrument will accurately record total fuel consumption as displayed in the totalizer window.





  16. #16
    Member AKBassking's Avatar
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    Default Can you Hear it?

    2005 Evinrude 250 with jet! I can hear the sucking action from my wallet to my gas tank to the engine!

    ALASKAN SEA-DUCTION
    1988 M/Y Camargue YachtFisher
    MMSI# 338131469
    Blog: http://alaskanseaduction.blogspot.com/

  17. #17

    Default

    Each one takes his own craft, lets you cover more water find the fish.
    Quote Originally Posted by Sierra Hotel View Post
    ROFL Alaskamokaiman! What about the four fishing buddies? Where do they sit?

    SH

  18. #18

    Default WOT etc.

    Any thoughts on cruising with the F115 above 4500rpm as far as wear and tear. I spoke with the mechanic at Deweys and he indicated that they have had problems with units that a charter operator ran who put a limiter on his motors so his captains couldn't run higher than 4500rpms. He indicated that was the cause of the mechnical problems and said these motors are built to run at high RPM all day.

    We were fishing out of Seward this weekend and I had six aboard with all our gear in a 22ET Searunner HT with a F115. Was running near WOT out and back at around 24mph. I realize that I could re-prop but most times there are only two or three on board and in good water I can run it at around 4400rpm @ 26mph which is fast enough for me.
    Ruby at the end of a good day.

  19. #19
    Moderator Paul H's Avatar
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    Default

    Another option for fuel flow meters, and relatively cheap is the Lowrance LMM-400. It's a bit over $150 with a fuel flow sender, or if you have a newer engine that will communicate with the LMF, you can just hook it up with an adapter and get fuel flow from the engine, as well as other diagnostics.

    I just ordered one for my suzi DF 140, but haven't had a chance to hook it up yet.

    As far as WOT running being bad for the engine, it is also related to how you are propped. If you are overpropped and running wot for extended periods of time, that's not a good thing long term.

  20. #20
    Member AKBassking's Avatar
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    Default

    Quote Originally Posted by Paul H View Post
    Another option for fuel flow meters, and relatively cheap is the Lowrance LMM-400. It's a bit over $150 with a fuel flow sender, or if you have a newer engine that will communicate with the LMF, you can just hook it up with an adapter and get fuel flow from the engine, as well as other diagnostics.

    Paul, do you mean the LMF-400? Where did you get it?

    ALASKAN SEA-DUCTION
    1988 M/Y Camargue YachtFisher
    MMSI# 338131469
    Blog: http://alaskanseaduction.blogspot.com/

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