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Prop characteristics
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| Joe Kriz |
Posted on 03/13/13 - 8:05 PM
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The Bigfoot is only 13 pounds heavier then the Mercury 60hp 4 stroke.
They both are the same length at 20 inch long shaft so one doesn't hang down lower in the water then the other.
See our article here on Engine Weights.
http://www.whalercentral.com/articles...ticle_id=5
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| Tom W Clark |
Posted on 03/14/13 - 8:35 AM
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Gearcases come in essentially three classes: Small, Intermediate & Large
The "Small" gearcases are broken down further into:
2.5" (portables that use through-hub exhaust)
3.0" (20-30 HP)
3.5" (up to 60 HP)
Intermediate size is 4.25" (40-130 HP)
Large size is 4.75" (usually 135 HP and up)
These dimensions describe the diameter of both the "bullet" of the gearcase and the hub of the propeller. These are nominal dimensions and you may find some small variation between different models but (with extremely few exceptions) an intermediate size propeller will fit an intermediate gearcase, a Large fits a Large gearcase, etc.
The idea of the BigFoot is that they put the gearcase of a large HP class and fit it to a smaller motor. In the case of the Mercury FourStroke BigFoot 60, they use the Mercury intermediate size gearcase which is used on their motor up to 115 HP and replace the small 3.0 gearcase used on the FourStroke 60. This allows a propeller with a larger diameter, and thus greater blade area, to be used.
Because the power is the same, 60 HP, the gearing is reduced (increased numerically) from 1.83:1 to 2.33:1
So now with a BigFoot, a larger propeller is turning at a slower speed which initially was intended for smaller motors on larger boats, like pontoon boats and work boats. But what many manufactures have discovered is that sometimes using a BigFoot model can be highly successful on smaller faster boats as well.
Suzuki has essentially adopted the low gear ratio/large diameter propeller idea to its entire line up. Yamaha offers many Hi-Thrust models which are just like Mercury's BigFoot. OMC, and now BRP has always had models with lower gear ratios and uses intermediate size gearcases exclusively all the way down to 40 HP even though they use the same gearcase on their 130 HP models. They don't bother to use Small gearcases on anything larger than 30 HP.
Boston Whaler started to equip some of their models with Mercury BigFoots when they discovered that they simply performed better on some of their boats, even though if you take Mercury marketing at face value (always a bad idea) they were clearly aimed at Pontoon Boats not Montauks.
The Dauntless 15 has a 20" (nominal) transom and uses a 20" (nominal) shaft outboard so a 20" FourStroke BigFoot 60 fits on the same boat as a FourStroke 60.
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| gary0319 |
Posted on 03/14/13 - 12:24 PM
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Tom W Clark wrote:
Suzuki has essentially adopted the low gear ratio/large diameter propeller idea to its entire line up. Yamaha offers many Hi-Thrust models which are just like Mercury's BigFoot. OMC, and now BRP has always had models with lower gear ratios and uses intermediate size gearcases exclusively all the way down to 40 HP even though they use the same gearcase on their 130 HP models. They don't bother to use Small gearcases on anything larger than 30 HP.
Since I started this thread I'll do a half hijack and ask a Suzuki question.
I've been reading up on all manner of 60hp motors in doing research on a possible repower for my Dauntless 15. The performance stats on the Suzuki 60 4 stroke are seemingly a lot better than any of the other manufacturers that I've looked at; both in terms of higer top end, and better mpg at optimal cruise. Now this is coming from the Suzuki web site so ??? But, if one is to belive the numbers, could the Suzuki gearing and prop thing have something to do with this? I really like the e-tecs, but the numbers on the Suzuki have certainly turned my head around.
Gary
Edited by Joe Kriz on 03/14/13 - 1:20 PM
1998 Dauntless 15 - 1998 Mercury 60 |
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| Tom W Clark |
Posted on 03/14/13 - 7:17 PM
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Gary -- I have never noticed that before. Can you cite an example of a Suzuki report and a competitor's report where the exact same boat is used?
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| gary0319 |
Posted on 03/14/13 - 7:29 PM
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Tom W Clark wrote:
Gary -- I have never noticed that before. Can you cite an example of a Suzuki report and a competitor's report where the exact same boat is used?
No, not on the exact same boat. But, even with different hulls of similar weights, the stats are so overwhelmingly in favor of the Suzuki that I couldn't help but notice. Surely, not very scientific, and leaves many questions (like the one you point out).
1998 Dauntless 15 - 1998 Mercury 60 |
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| Commander Coo1 |
Posted on 03/20/13 - 10:19 AM
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The only test i recall seeing with the same hull were with an E-TEC 175 and a Suzuki DF175 on a 2008 Dusky 203.
E-TEC cruised at 31.3mph/4.0mpg, Suzuki cruised at 24mph/3.7mpg or 29mph/3.6mpg. E-TEC top end was 44.5 mph and suzuki top end was 46.1mph. looks like the tests were pretty similar setup except the suzuki was tested in 68* air and the E-TEC in 95* air. I dont know if this will transfer down to the 60hp class at all but it was interesting to read for me when i re-powered with a 175. I wonder if the E-TEC would have performed better with a Rebel instead of the Viper it was tested with.
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| gary0319 |
Posted on 03/20/13 - 12:53 PM
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Closest comparison on the 60 hp seems to be on a 16 foot Alumacraft. The links below are to the pages for the Etec and the Zuke. The Alumacraft model names must have changed between the years but the boat specs are the same. Information is from the respective manufacturers web sites. What interested me is that the dry weight of the Alumacraft is pretty close to my 15 Dauntless.
http://www.evinrude.com/Content/Pdf/n.../PE924.pdf
http://www.suzukimarine.com/Product%2...CS%20DF60A
1998 Dauntless 15 - 1998 Mercury 60 |
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| Joe Kriz |
Posted on 03/20/13 - 1:36 PM
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gary0319 wrote:
Since I started this thread I'll do a half hijack and ask a Suzuki question.
I've been reading up on all manner of 60hp motors in doing research on a possible repower for my Dauntless 15. The performance stats on the Suzuki 60 4 stroke are seemingly a lot better than any of the other manufacturers that I've looked at; both in terms of higer top end, and better mpg at optimal cruise. Now this is coming from the Suzuki web site so ??? But, if one is to belive the numbers, could the Suzuki gearing and prop thing have something to do with this? I really like the e-tecs, but the numbers on the Suzuki have certainly turned my head around.
Gary
This video shows identical boats going head to head with some other brands of new motors.
http://www.youtube.com/watch?v=Rfm64x...e=youtu.be
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| gbollin |
Posted on 03/21/13 - 5:20 PM
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Joe and Tom: Thanks for your detailed responses to my novice questions. The information has made me reconsider my plan for repowering my Dauntless 15, now I'm uncertain which 60 hp Merc to use. Tom - you noted that a Bigfoot could be highly successful on a smaller boat, and some boats simply perform better with a Bigfoot. I assume this means more than just top speed, based on other discussion in this thread. What specifically do you mean by better performance? Can you compare the differences to be expected between a Dauntless powered with a Bigfoot and one powered with a standard Merc 4-stroke? Thanks.
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