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matt_unique
Joined: 27 Feb 2007 Posts: 1881 City/Region: Boston
State or Province: MA
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: Napoleon
Photos: Napoleon
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Posted: Fri Apr 25, 2008 4:38 pm Post subject: Tomcat fuel capacity vs. gauge readings |
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Well I added my first fuel to the Tomcat yesterday. Just over 32 gallons for $111 - party!
My port tank read E and my starboard tank read 1/4. I added 20 gallons to my port tank and the gauge moved to 1/2. I added 10 gallons to my starboard tank and it went from 1/4 - 1/2. It would appear my gauges reflect only 40 gallons in each tank. Do others have the same experience?
I noticed the fuel gauge goes far below E when the power is shut off. Perhaps it goes quite a bit past F as well to account for the full 75 gallons each tank is supposed to hold?
Thanks for the help. _________________ Captain Matt
Former owner of Napoleon (Tomcat) Hull #65 w/Counter Rotating Suzuki 150's. |
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Al & Pat Parker
Joined: 05 Aug 2007 Posts: 76 City/Region: New Bern
State or Province: NC
C-Dory Model: 25 Cruiser
Vessel Name: Knot Home
Photos: Knot Home
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Posted: Fri Apr 25, 2008 9:12 pm Post subject: |
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Hi Cap,
Well, ours is a CD25, but we had a similar problem. 100 gal tank, only took 63 gal brand new from the dealer, full to overflow, and full on the gauge. Ran it to show empty, filled it again, 63 gal. We could never figure it out until the dealer gave me a new sender, an aftermarket "universal" one. I installed it per the directions, it cured the problem. Ran it to empty on the gauge the 3rd time & put in 87 gal.
I measured the tank, it's 100gal. It was within a cupla inches of the top when full, only thing we could figure was that there was fuel in it when it came from the factory (very hard to believe), and the gauge read empty.
Who knows, strange things happen. Things don't fail in tandem, but maybe you got 2 bad senders. _________________ Al & Pat
C-D 25 "Knot Home"
Mainship Pilot 30 "Juust Right"
on the Neuse River at New Bern
W8UT
www.boatanchors.org/C-Dory25.htm
"there is nothing -absolutely nothing- half as much worth doing as simply messing about in boats."
(ratty to mole, Wind in the Willows) |
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matt_unique
Joined: 27 Feb 2007 Posts: 1881 City/Region: Boston
State or Province: MA
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: Napoleon
Photos: Napoleon
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Posted: Fri Apr 25, 2008 9:55 pm Post subject: Gas |
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I have a feeling it's just a sending unit with a limited range of motion. With the power off, the gauge moves a significant distance past E.
Thanks for the reply. |
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forrest
Joined: 02 Nov 2003 Posts: 381 City/Region: Chehalis
State or Province: WA
C-Dory Year: 2007
C-Dory Model: 26 Venture
Vessel Name: Long Story
Photos: Long Story
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Posted: Fri Apr 25, 2008 11:04 pm Post subject: |
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I suspect the sending unit is not long enough for the depth of the tank. For instance if you have a fifty gallon tank that is ten inches deep and a sending unit that is only eight inches long, the gauge will read empty with only seven inches (35 gallons) of fuel consumed. You will still have three inches of fuel left (15 gallons) but since the sending unit is completely extended down it will show the tank to be empty. Run the boat until it starts starving for fuel and keep track of when the gauge said empty and how much fuel you have burned since it said empty and you can figure how far off the bottom the sending unit is.
Forrest |
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Doryman
Joined: 03 Oct 2006 Posts: 3807 City/Region: Anacortes
State or Province: WA
C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: Lori Ann
Photos: Lori Ann
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Posted: Fri Apr 25, 2008 11:24 pm Post subject: |
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Just be glad you actually have a fuel gauge. I don't! I use my Yamaha gauges to show me how much fuel I have used and subtract that from 150.
Warren _________________ Doryman
M/V Lori Ann
TomCat 255, Hull #55, 150 Yamahas
Anacortes, WA
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Larry H
Joined: 02 Nov 2003 Posts: 2041 City/Region: Tulalip,
State or Province: WA
C-Dory Year: 1991
C-Dory Model: 22 Cruiser
Photos: Nancy H
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Posted: Sat Apr 26, 2008 12:09 am Post subject: |
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IMHO the marine fuel senders and gauges are not very accurate.
The senders have to be adjusted for various tank depths and the sender/gauge combination is not linear.
I started with empty tanks and filled to the 1/4 mark on the gauge, noted the gas pump reading, filled to 1/2, noted the pump reading and so on till full. My 25 gal tanks on my CD 22 actually held about 9.5 gallons at the 1/4 mark! The newer translucent tanks on the 22's can be read by looking at the fuel level. A much better idea.
Too bad that won't work on the 25's and 255's. _________________ Larry H
A C-Brat since Nov 1, 2003
Ranger Tug 27 ex 'Jacari Maru' 2017 - 2022
Puget Trawler 37 ex 'Jacari Maru' 2006-2017
1991 22' Cruiser, 'Nancy H'--1991-2006 |
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matt_unique
Joined: 27 Feb 2007 Posts: 1881 City/Region: Boston
State or Province: MA
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: Napoleon
Photos: Napoleon
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Posted: Sat Apr 26, 2008 8:17 am Post subject: Gauge |
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I agree - I prefer to be able to put a stick into my tanks and forget fuel gauges all together. Of course on our boats this is impossible.
Ha ha - maybe I'll bring 10G aboard and run her dry sometime to learn how to read the gauge.
Thanks for the replies. |
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Pat Anderson
Joined: 02 Nov 2003 Posts: 8555 City/Region: Birch Bay, WA
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 25 Cruiser
Vessel Name: Daydream
Photos: Daydream and Crabby Lou
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Posted: Sat Apr 26, 2008 10:19 am Post subject: |
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We have found the in-dash fuel gauge on Daydream is totally worthless - the Navman fuel computer fuel used/fuel remaining readings on the other hand while not perfect are quite accurate. A very worthwhile addition. _________________
DAYDREAM - CD25 Cruiser
CRABBY LOU - CD16 Angler (sold 2020)
Pat & Patty Anderson, C-Brat #62!
http://daydreamsloop.blogspot.com
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garyk
Joined: 19 Feb 2007 Posts: 70 City/Region: Ketchum
State or Province: ID
C-Dory Year: 2006
C-Dory Model: 255 Tomcat
Vessel Name: AMIGO 11
Photos: Amigo II
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Posted: Sat Apr 26, 2008 11:28 am Post subject: |
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There is considerable difference in our gauge reading when cruising and when drifting or at the dock. We will read 1/4 at cruise and flat empty at the dock. The cruise reading is the more accurate. While making two trips to Alaska this past two summers, we have had lots of opportunities to check fuel consumption. I find our gauges are quite accurate when predicting how much fuel will be needed to top off, and how much remaining at a given gauge reading. This information is good only for this boat. Each boat will differ for reasons noted in this thread.
I would suggest making note of gauge level before fueling, guess how much it will take to top off (each side), after a few trips to the fuel dock you should have a good idea of FUEL REMAINING, at a given reading on each tank. I like to give a 10% reserve and when estimating fuel needed for a given leg I use 1.7 mile per gal. for our two 150 hp. Honda engines @ a cruise speed of 22 to 25 mph. Tide in Alaska can have a effect on the numbers but can easily be calculated.
Take time to know your boat, keeping a good log will give a reference to come back to if you feel thing are changing. |
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JamesTXSD
Joined: 01 Mar 2005 Posts: 7446 City/Region: from island boy to desert dweller
State or Province: AZ
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: "Wild Blue" (sold 9/14)
Photos: Wild Blue
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Posted: Sat Apr 26, 2008 2:05 pm Post subject: |
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According to FAA regs, the only time a fuel guage in an aircraft has to be accurate is when it reads empty! I don't know if there's a corresponding rule for boats. Our fuel gauge was off from day one - never showed full, even when we had fuel running out the vents. Within a few months, it completely quit. We spent last winter cruising in the Keys without a fuel guage; we based our estimated fuel burn on engine hours, and it came out pretty close to actual (and, we never ran out, but always had a 5 gallon spare available, just in case).
We had a fuel flow meter installed, and it is very accurate. At the same time, that Honda dealer replaced our fuel gauge (under warranty), and it has been working fine since. So, we went from one unreliable/non-functional unit, to two working units. I also use the fuel flow meter to trim or adjust throttle for best fuel burn - and that has been the absolute best usage of that instrument.
Yesterday, we cruised around at 1800 RPMs, burning just under one gallon per hour. 2000 RPMs increase that fuel burn to 1.5 gallons per hour with a negligible increase in speed. Same holds true when running in the mid-teens (after getting up on plane) - we get better mpg at 15-17 knots than 12.5-13 (on plane, eased back).
For now, you can get a fuel burn estimate from the manufacturer's site (or one of the boat test sites), and go from there.
Of course, YMMV! (sorry)
Best wishes,
Jim B. _________________ Jim & Joan
CD-25 "Wild Blue" (sold August 2014)
http://captnjim.blogspot.com/
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thataway
Joined: 02 Nov 2003 Posts: 20829 City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
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Posted: Sun Apr 27, 2008 6:23 pm Post subject: |
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Go buy the Lowrance fuel guages...Only about $150 for the two engines, and you will have peace of mind. The float senders are not accurate, as most above have noted. (Navman/Northstar are very similar)--but Lowarance have many more functions, with the Suzuki engines. _________________ Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL |
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billtwymank
Joined: 15 Oct 2010 Posts: 158 City/Region: Pinehurst - New Bern, NC
State or Province: NC
C-Dory Year: 2008
C-Dory Model: 255 Tomcat
Vessel Name: Lady KC
Photos: Lady KC
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Posted: Fri Apr 22, 2011 10:51 am Post subject: Fuel Useage-Flow Meter on TomCat |
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Morning..........
I am a bit confused about the fuel consumption on our TomCat equipped with two 2008 Honda 135's.,
as we do not have a fuel flow meter.
(we have been on the Honda web site and there is a fuel management digital gauge that can be installed)
I have read several C-Brats pages on all of these subjects.
With a little chop on the water and both engines running at 4000rpm, I had Lady KC going about 22mph per our Garmin-450 GPS,
but I sure didn't know how much fuel I was using as the gauges provided by C-Dory were very questionable when underway.
If I remember correctly, I believe the previous owner told us that he used about 5 gal per hour running at 23mph.
This means I should be able to travel 250+ miles on 60 gals. per engine.
Per some of the C-Brat input I am not sure how to interpet and calculate how many miles I can travel on 120 gallons of gas at 4000 rpm (60 gal. per engine).
[color=redQuestion------[/color]
***Can any TomCat owner provide me with some input on this subject of "gallons used per hour"?
x _________________ Bill & Karan
Lady KC |
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Dreamer
Joined: 01 Jan 2006 Posts: 1764 City/Region: Really Sunny SaddleBrooke
State or Province: AZ
Photos: Dreamer
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Posted: Fri Apr 22, 2011 12:18 pm Post subject: |
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Billy,
Unfortunately, he was quoting fuel use per engine
At 23 mph, you'll probably use 10-11 gph. At 21 kts, if lightly loaded, we use 11 gph with Honda 150s.
The fuel gauges are pretty accurate with the Honda digital gauges. We usually work off the top half of the tank and fill up. The mpg feature is way off because the gauge uses the pitot pressure for a speed indicator. The gph figure seems right on. _________________ Roger
Once a C-Brat, always a C-Brat
Dreamer- Sold 25 Feb. 2013 |
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thataway
Joined: 02 Nov 2003 Posts: 20829 City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
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Posted: Fri Apr 22, 2011 3:18 pm Post subject: |
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I think that the boats with Suzuki 150's run a little faster (and do run lower RPM at the lower cruising speeds--I am about 3200 at 22 mph. I get close to what Roger gets at that speed--about 10 gallons an hour, both the external flow guages and with fill up to fill up.
Figure 2 miles per gallon for both engines (you should do a little better than that, but that gives you a safety margin.)
The 255's hold 150 gallons (a little less is usable)--but a range of 250 is very do-able in almost any conditions and 300 miles in ideal conditions. Your Honda 135's--which will burn the same amount of fuel as Roger's 150s at that speed. |
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Pacificcoast101
Joined: 29 Sep 2007 Posts: 717 City/Region: Torrance
State or Province: CA
C-Dory Year: 2008
C-Dory Model: 255 Tomcat
Vessel Name: No Pressure
Photos: No Pressure
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