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Sno' Dog Log
Performance Figures & Technical Stuff
Sno' Dog is a 2006 model PDQ 34 Powercat (Hull #87) with twin counter-rotating Yanmar Model 4JH3-HTHE Engines rated at 100 HP @ 3800 RPM (continous for 1 hr) fitted with ZF model ZF-25 Hydraulic Transmissions. Total weight of each engine/transmission is 259 kg or 571 pounds. The (Factory-installed) Propellers on our boat are (were): 17-in dia x 14-in pitch x 3-bladed - counter-rotating.
These numbers reflect ideal conditions. Range would, no doubt, be reduced in
open sea and/or rough conditions.  For an open water passage, I'd certainly want to
allow a healthy safety margin.  Hopefully, by the time we attempt our first long passage
in
Sno' Dog, we will have gained much more experience and be able to refine this chart further.
    Port          Date      Log       Eng Hrs   Gallons    GPH      MPG    Ave Spd   Cum GPH  Cum MPG  Cum Spd
   Whitby         5/17       10(E)       10.2         (Full)          -           -             -                 -                 -                   -    
   Ottawa         5/25         ?            40.5         83.7        2.76        ?            ?             2.76
  Burlington     6/13         ?            66.9        110.0       4.15        ?            ?             3.42
Mamaroneck   6/17         ?            92.7        104.6       4.04        ?            ?             3.61
  Newington     6/27         ?          121.0        106.0       3.76        ?            ?             3.65
   Belfast         7/15      1289        155.6          97.7       2.82       ?             ?            
3.45           2.55          8.8 kts
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When we first chose the PDQ 34, we were a bit concerned about the fuel and water (and holding) tank sizes, but so far they've proved entirely adequate. Now that we've calibrated the gauges, we feel more comfortable using more of the available liquid before refilling. On our Maine cruise, we went 35 hours - and about 250 nautical miles - before refueling with 98 gallons. This works out to 2.6 nm/gal.  At this rate, assuming a total usable fuel capacity of 165 gal, our range would be 425 miles.  Since our cruising was a mixture of leisurely 7-kt runs interspersed with 16-kt sprints, there's little doubt that we could easily extend our range to over 500 nautical miles if needed. To me, this seems entirely adequate for this kind of boat.
What you can see from the above table is that fuel consumption does vary somewhat.  Although it doesn't really show above, I know that the lower fuel consumption figures reflect the portions of our travels where we slowed down a bit, whereas the higher numbers reflect mostly fast (15-16 knot) traveling.  Also, no allowance has been made for generator fuel consumption.  (I think we've got just over 20 hours on the generator now).                         HMC    07-30-06
My best guess (engineering approximation) at present is that we burn about 2 gal/hr at 7 knots and perhaps 6 gal/hr at 16 knots.  If we slowed down a bit, we could improve on these numbers.  Based on experience to date, here are my best estimates:  (Range assumes 160 gallons usable fuel.)
         Speed               RPM         Gal/Hr        NMi/gal        NMi Range
   6.5 kts  (7.5 mph)        1400          1.8             3.6                  575
   7.3 kts  (8.4 mph)        1600          2.2             3.25                525 
  15 kts  (17.2 mph)        3100          6.0             2.5                  375
  16 kts  (18.4 mph)        3250          7.0             2.3                  345
      Port          Date     Log    Eng Hrs   Gallons   GPH    MPG   Ave Spd  Cum GPH  Cum MPG  Cum Spd
Newington     10/04    1523     186.6        78.2        2.52       3.0         7.5            3.31           2.60           8.6
At. Highlands 10/07    1806     211.6      108.6        4.34       2.6       11.3           3.44            2.59            8.9
Annapolis       10/10    2035     233.6        93.0        4.23      2.5        10.4           3.51            2.58            9.1
   Norfolk         10/14    2167     244.9        47.4        4.14      2.8        11.7           3.55            2.59            9.2
Beaufort NC    10/18    2346     262.4        60.0        3.42      3.0        10.2           3.54            2.62            9.3
Georgetown    10/22    2514     279.2        59.2        3.52      2.85      10.0            3.54            2.63           9.3
Thunderbolt    10/24    2661     291.6        57.2        4.61      2.6         11.8           3.59            2.63           9.4
Ortega (JAX)    10/27    2807     304.5        55.1        4.26      2.7        11.3            3.62            2.63           9.5
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  The latest Performace UPDATE - as of 11/04/06 - for Sno' Dog's Fuel Consumption and Mileage...
Note: All values are in Nautical Miles (Knots). To convert to Statute Miles, multiply by 1.151
  03-07-07 - Powerboat Reports published a review of the PDQ 34 in their March 2007 issue.
                  
Click here to see that review.  Or, view a reasonable facimile of the report simply by clicking here.
                   If you'd rather have a copy of the full article via e-mail (incl links to the attachments) just
e-mail me.
                    Finally, if you would like to you view the
Powerboat Reports Performance Tables (which agree
                   closely with our experience to date) just
click here.
Counter
We were not able to activate our Distance-over-the-Ground Log properly until July 15th.
For this trip - tabulated above - from Newington (Portsmouth) NH to Ortega (Jacksonville) Florida, the figures are:
Total Distance traveled:
1284 n mi (1478 st mi). Engine hours: 118 hr. Fuel Consumed: 480 gallons.
This works out to: Average Speed:
10.9 knots (12.5 mph).  Average Fuel Usage: 4.07 gallons/hour
Average Mileage:
2.7 nautical miles per gallon (3.1 statute miles per gallon).                                    HMC 11/04/06
click for larger image
  06-30-08 - Update, June 2008...
                                                   
We've now got data from over two years of operation. Performance continues
   very similar to that outlined above.  Looking through our complete table of Fuel Consumption, I see that the longest
   distance we've traveled so far between fill-ups is
345 nautical miles (397 statute miles).  We have gone a maximum
   of
56.5 hours between fill-ups and the most fuel we have taken on at a single fill-up was 131.2 US gallons.

  
As expected, our mileage has varied somewhat with speed. Our worst mileage (2.25 n mi/gal) was recorded when
   our average speed was
11.8 knots, although for this segment our fuel burn was only 4.6 gal/hr.  The best milege
   we've seen was
3.35 n mi/gal with a fuel burn of 1.69 gal/hr, in this case our average speed was a mere 5.7 knots
   (See my comments below regarding powercat efficiency at speed versus a monohull design.)

  
As of our last fill-up in Newport, RI on May 26, 2008, total cumulative Sno' Dog statistics since we took delivery
   on May 15th, 2006 are as follows:
Total engine hours: 878 hrs
                                                   
Total mileage logged: 7936 nautical miles
                                                   
Total fuel consumed: 3,141 US gallons
   Computed Averages are:   Average Fuel Consumption:
3.35 gallons per hour
                                            Average Speed:
9.0 knots
                                            Average mileage:
2.54 nautical miles per gallon (2.92 statute mi/gal)

  
One final observation about cruising range  Although this boat gets great mileage, I think her useful range has been exaggerated a bit in PDQ's promotional literature.  To begin with, the actual fuel capacity is somewhat less than advertised.  We asked PDQ to calibrate our fuel tanks when they first filled them at the factory, which they did.  Their notes showed that it took a total of 176 US gallons to top off the tanks, starting with bone dry tanks.  Obviously, the fuel pick-ups are located somewhat above the bottom of the tanks, so I wouldn't count on much more than 150 gallons usable.  Realistically, I'd say our range - cruising at 15 knots - is about 360 nautical miles.  If we reduce speed to 6.5 knots, we could likely increase this to 550 nautical miles, but that's about it. (And that assumes reasonably calm water.)

   
On the positive side, our Sno' Dog has the ability to cruise at speed with a very minor mileage/range penalty compared to a conventional monohull.  As an example, consider the Camano, a popular semi-displacement fast trawler.  At displacement speed (7 knots) the Camano 31 burns just over one gallon per hour giving her a range of 800 nautical miles. BUT, if you bring her up onto a plane and run at 15 knots, fuel consumption jumps to over 9 gallons per hour - and range drops to a mere 180 nautical miles! (See Powerboat Reports test data in the May 2007 issue.)
This HUGE drop in efficiency at speed is typical of virtually all monohulls when driven above displacement speed.  The powercat is the only design I'm aware of that can run at speed with such great efficiency.  With fuel now approaching five dollars per gallon, this is becoming a very endearing characteristic indeed!

   
We continue to be thrilled with the PERFORMANCE of our PDQ 34.
I wish we had FloScan gauges so we'd know our exact fuel consumption at various speeds - I'm seriously considering installing them (but they're quite expensive and complicated for twin diesels).
What we do know is
average fuel consumption. Here's what it looks like to date (07/30/06):
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.
The "canoe stern" design of the PDQ
           yields excellent efficiency at
                 speeds in the mid teens.
Click on photo for larger image
PS: Feedback from PDQ owners on this subject is appreciated - how do your numbers compare?
Our starboard propeller upon haul-out in NH in June 2008
On our trip North this spring, starting back in the Chesapeake Bay on May 21st, we noticed a vibration.  When we hauled out in New Hampshire to check the zincs, this is what we found (photo on left). I'm sure our mileage for the last 10 days of the trip might have been better without this rope wrapped around our prop!  If the weather hadn't suddenly turned so cold, I might have been more inclined to dive down and check it out,  I wasn't quite prepared to deal with 48-degree water (see Page 4).
Rope around the prop!
    (
Click for larger image)
Note: I have moved the older entries from this page to the bottom.  Starting here, are the original entries dating back to July 2006, a mere two months after we took delivery of Sno' Dog.
07/06/08 UPDATE -  Being an engineer, and prompted by recent posts on PDQ Forum, I decided it was time to update the figures on this page.  Although we still don't have exact fuel burn data, we do have two years of  information on Sno' Dog.  Using data from our log, combined with Yanmar and Powerboat Reports fuel burn data, I was able to construct the table below.  The numbers shown apply to Sno' Dog with a reasonably clean bottom, nearly full fuel and water, and a moderate amount of cruising gear aboard.  High-end performance is noticeably weight-sensitive, our top speed increases by about one knot when fuel gets down to 1/4 full.  Also, we try to use fuel in our forward tank first as this improves performance.
Note: I have moved the tabulations of our earlier data - going back to May 2006 - to the bottom of this page.
To better visualize the data in the table above, I plotted it in graphical form - here's the picture...
Looking at this graph you can see that boat speed increases fairly linearly with with engine speed up to about 7 knots (1600 RPM) then it starts to level off.  Fuel consumption, however continues to increase steadily with RPM causing in a drop-off in milage (and range).  But, once the boat reaches 10 knots or so (2400 RPM), she begins to plane and speed picks up resulting in a flatening of the mileage curve.  Clearly, there's not much point in cruising in the 8 to 12 knot range as there's little fuel saving to be had here.  This is something we noticed qualitatively early on. The boat accelerates easily to 7 knots at a mere 1500-1600 RPM.  (At this speed - which feels like a fast idle - the boat is so quiet we're always surprised to see a 7+ kt reading on the GPS.)  But, much like a planing, or semi-displacement monohull, increasing the throttles from 1800 to 2800 RPM increases the wake size but does not to offer a commensurate speed increase.  Once above 2800 RPM, however, the boat feels as though she's planing, the bow actually comes down a bit and the wake gets smaller. For this reason, we normally avoid extended cruising in the 2000-2600 RPM range.  For Sno' Dog, our most economical high-speed cruising occurs at about 3000 RPM which, depending on load, produces a speed of 14 to 15 knots.  Speeding up to 3200 (about 16 knots) however results in a very modest milage penalty and we do this often if we are in a hurry.

Conversely, better mileage can be obtained by slowing down, but to realize significant improvement, we have to slow down to about 7 knots (1600 RPM) .  If we really want to maximize mileage - and range - it appears that we should run below 6 knots (1200 RPM).  At this speed we could theoretically go 620 nautical miles on a single fill-up.

Finally, there's been an ongoing discussion about the possible fuel saving of single-engine operation.  The PDQ is quite capable of running on a single engine.  Even though the other propellor will freewheel, I am told that the cutlass bearing will fare just fine (which is not true of all twin screw designs).  So the question is, how much fuel might we actually save by doing this?  With all the data shown above, it is now possible to comment on this.  The only missing information is speed and RPM for single-engine operation.  Fortunately (being an engineer and all) I just happen to have some data on this.  Plugging in the fuel burn numbers from the table above, we can generate the following mini table:
                    
Twin Engine Performance                                Single Engine Performance
    6.5 kts  -  1400 RPM  -  1.70 gal/hr - 3.9 n mi/gal         2000 RPM  -  1.5 gal/hr  -  4.3 n mi/gal
    7.0 kts  -  1500 RPM  -  1.85 gal/hr - 3.8 n mi/gal         2400 RPM  -  2.0 gal/hr  -  3.5 n mi/gal

As I suspected, the numbers come out awful darn close!  It looks as though a small saving might be had if you keep your speed below 6.5 knots.  I gather the consensus in the powercat design world is that variable pitch (feathering) propellers are necessary to realize meaningful savings from single engine operation.  But it does appear that, at least at slow speeds, we might be able to save a little bit with our PDQ - and certainly we'd cut down on engine time and associated maintenance.  I'm sure this discussion will continue, but that's my two cents for now.           HMC 07/07/08
    ENGINE               SPEED                  FUEL BURN                          MILEAGE                             RANGE (150 Gal usable)
 
   RPM         in MPH    in Knots         Gallons/Hr          Stature Miles   Nautical Miles      Stature Miles   Nautical Miles
       800             4.4             3.8                    0.8                          5.5                      4.75                       820                     710
     1000             5.6             4.9                    1.1                          5.1                      4.45                       765                     665
     1200             6.7             5.8                    1.4                          4.8                      4.15                       715                     620
     1400             7.5             6.5                    1.7                          4.5                      3.9                         675                     585

     1600             8.3             7.2                    2.0                          4.2                      3.65                       625                     545
     1800             8.7             7.6                    2.3                          3.8                      3.3                         570                     495
     2000             9.2             8.0                    2.7                          3.4                      2.95                       510                     445
     2200             9.9             8.6                    3.2                          3.1                      2.7                         465                     405
     2400           10.8             9.4                    3.7                          2.9                      2.5                         430                     375
     2600           12.7            11.0                   4.3                          2.9                      2.5                         430                     375
     2800           14.6            12.7                   5.1                          2.9                      2.5                         430                     375
     3000           16.6            14.4                   6.0                          2.8                      2.4                         415                     360
     3200           18.0            15.7                   7.1                          2.5                      2.2                         380                     330
     3400           19.4            16.9                   8.4                          2.3                      2.0                         345                     300
     3600           20.6            17.9                   9.7                          2.1                      1.85                       315                     275
   3800/WOT   21.8            18.9                 11.0                          2.0                      1.7                         290                     255
04-17-10
    ENGINE                          SPEEDS                 
      RPM                              in Knots

                       3-BLD PROP     4-BLD PROP__  Difference__

       800                    3.8                   
3.9                   +0.1
     1000                    4.9                   
5.0                   +0.1
     1200                    5.8                   
6.0                   +0.2
     1400                    6.5                   
6.8                   +0.3
     1600                    7.2                    7.4                   +0.2
     1800                    7.6                   
7.7                   +0.1
     2000                    8.0                   
8.0                       0
     2200                    8.6                   
8.6                       0
     2400                    9.4                   
9.4                       0
     2600                  11.0                
12.5                   +1.5
     2800                  12.7                
14.3                   +1.6
     3000                  14.4                
15.6                   +1.2
     3200                  15.7                
16.9                   +1.2
     3400                  16.9                
18.2                   +1.3
     3600                  17.9                
19.4                   +1.5
      WOT                 18.9 @3800  
20.4@3750      +1.5
 
Test cond's: Main Tank 5/8 full, Fwd Tank 3/8 full, Water 1/2 full,
  Temp 78 F, Seas: less than 1 foot,  Bottom: clean (freshly painted).
04/17/10 - New 4-Bladed Propellers - Test Results:
New 4-bladed prop installed on Sno' Dog.
The new propellers feel smoother at all speeds, but there is a slight vibration noticeble around 2000 RPM. (We seldom cruise at this speed anyway.) Speedwise, there is a substantial improvement once the boat comes onto plane.  At our normal (fast) cruise setting of 3000-3200 RPM, we have gained over a knot of speed.  At wide-open-throttle (WOT), the boat runs 1.5 knots faster than she did before.  WOT engine speed is 3750, a bit less than our previous 3800 RPM.
Needless to say, we are very happy with these results!
Props are 17" dia x 14" pitch
  
(same as the 3-bladers)