How much Fuel Do You Have????

S

Stanley-J

New member
Is it just my CD or does others have the same problem?
I can go from a 1/2 tank to close to empty on my gauge depending on the boats plane angle. I assume the tanks have baffels inside but my gauge changes significantly as the angle changes. I even though of putting in a dip stick in the tank to be sure of my fuel amount. I do carry a extra 5 gallons of fuel just in case but I sure would like to know if I'm the only one or what.
 
Hey Chuck ! To the best I can tell....gas gauges on boats are to do noting but give the folks practice drilling holes in your dash for things that really work. You are target on with the dipstick idea but be sure to check it when sitting still....or just drifting and not up on plane... Then...if you run out of fuel when on plane.....stick it again to see how much fuel you will have to just idle in to get more fuel. Some tank/boat set ups will give you just a bit of idle time....when it will not feed the small amount of fuel to your engines while on plane... but... it might be just enough to get you over to the bank on the river rather than just drifting down stream to the next county...or state depending on the river.

If you have an hour meter...and want to take the time to keep track of the hours on your motors each time you top off (again...if you refuel in the same exact spot each time...it will be more accurate... particuarly if you refuel in the water...or....on the trailer...more so on the trailer due to the contour changes at the stations.).... Now from here....after you use your boat in different conditions.... (cruising most of the time on smooth water.... cruising on your "local waters.... or just how much time did you spend just trolling along).... you will ge a pretty good idea of how many gallons per hour (on the motor hours....not the clock) you burn. Again...many variables here....

You might also want to take a look at some of the photo and see how some folks can "see their fuel levels" even underway....if you have a "clear" or transparent tank.... If you have a metal type tank.... go back to the stick idea....and simply do some "trials".... You might be able to borrow someone's little 3 gallon kicker tank....and just put one gallon at a time in it..... keeping up with distance traveled with a GPS...and run the boat at the different "500" RPM increments.... to get an "idea" of where your sweet spot is.... then.... after you have the 500's blocked and charted..... test it some more if you care to with smaller increments.....to really know where your optimal cruising speed is...

or... just keep an extra can of fuel on board. :smile :thup

Or... like some of the others of us...go ahead and bite the bullet and get a flow meter.... several threads already on line about those...and some of our folks have found some pretty surprising stuff about their exact hull and where the "sweet spot" for the most economical cruising is. It is not at 3500 on most C-Dory boats.
 
Thanks for the input guys, I'll try and check next time I put fuel in it and see if it shows the amount of gallons I dump in. The hundred gallon tank may only see 50 gals with the price around $3.00 a gallon, so I'll check and see if it shows around half full.
Another question ....I notice the smell of gasoline a lot in the cockpit coming from the fuel tank vent. Because this is my fist gas engine boat, is that normal?
 
Stankey-J

No, it's not normal to smell gas from the fuel tank vent(s). Not a lot, nor all the time, anyway. Maybe a little just after fill up, of course.

Are you sure it's coming from the vent?

Do you notice it just after fill-up, or all the time?

The intake hoses and vent hoses should have tight double clamps of stainless steel at both ends, as should the supply hose(s) to the engine. Check all these clamps for tightness.

Check your fuel filter and all the fittings, too. Add to that the tank switch, and the fuel gaugue sender units.

The Neoprene hoses get old fairly quickly, and should be replaced periodically. Some think they should be replaced every 5 years (!)

The hoses have their year of manufacture on them so you can tell their age.

Any fuel hose that is placed in a permanently bent/crimped position will crack along the lines of stress in a few years. For this reason, all bends must be gentle and rounded---no kinks.

Hope this helps!

Joe.
 
Stanley, yes check your inlet and vent hoses as Joe suggested. Also your sending unit gasket integrity under the forward access port in the cockpit. Then look at the tank engine hose fittings from inside the starboard large hatch looking towards the rear of the tank.

If you haven't done it already, you need to cut an access hole in the fiberglass shroud covering your inlet and vent hoses. I just did mine about 2 months ago, see pictures. Thought I had a 'completed' picture with port hole in place, but couldn't find it.

On the sending unit accuracy. I have the plastic gas tank and it 'bends' and distorts with temperature and amount of fuel, this causes great inaccuracies on the float readout sent to the dash. And as you found out, fore/aft boat attitude also greatly affects since the sending unit is near the rear edge of the tank -- would have been more accurate in the middle (fore/aft). I tend to go by nmiles driven, a stick sounds not too bad...
 
For what it's worth, here's my experience on a C-25:

Drained the gas tank in San Diego before I left, gauge read empty.
Got to Olympia, Wa, and filled the gas tank. Took 15 gal to the 1/4 mark, 80 gal to the full mark, 85 gal dumped fuel out of the vents (at $3.14/gal.) Been running for a couple of days, and the needle hasn't moved off full yet. So, the conclusion is: 1. The gauge is extreamly non-linear, and 2. If the tank is full enough you're dumping the stuff on the ground (we were in a gas station, not a fuel dock.)

On the subject of mileage, the boat is loaded to the gills for the summer voyage. So at 13 knts I think I get 2.5 mpg. At 6 knts, I get 7 mpg. If you see a C-25 going slow in Puget Sound, San Juans, etc., wave cause it's Journey On.

Boris
 
For all 3 1/2 yrs of ownership I've been trying to calibrate my gauge by noting the fuel reading in the water right at the ramp, then again on land, then filling tank to see how much was used. Results -- inconclusive, depends on temperature too. I figure at about 1/2 tank reading I'm down only about 35 gals, but that varies nearly 25%!

I agree with Boris, very NON-LINEAR, but also just plain inaccurate. Stick sounding better and better.
 
After owning 4 boats of various sizes/construction I have never yet had one where the fuel gauge worked! And I don't expect the C-Dory to be any different. I do plan on putting spy tubes on the C-Dory so I can at least see somewhat how much fuel I have.

On my sled the ONLY way the gauge works is sitting still with the boat in the water. Anything else and the gauge just bounces from full to empty! I would far prefer to have plastic tanks that you can see through enough to know how much fuel you have left.
 
Thanks for the info Joe. I do smell it most of the time. I did change the fuel filters but I checked them for leakage and there dry. The under cockpit floor doesn't smell when I open any access hatches, but when I'm standing by the vent side of the cockpit I do smell fuel. There is no access to anything other than the filters and the fuel sending units. I called the Factory and asked if they had any pictures of tank and line locations before I start cutting the deck to gain access but they said no. I'll try again to follow the lines, but maybe I'll block the vent and see if it goes away while I'm on the hard.
 
I launched my new CD 25, and the first thing I noticed was that the gas gage didn't work. A trip back to Cutter Marine plus some helpful discussions with their mechanic revealed what many already have mentioned; all gas tanks have "features", and mine is no exception. My metal tank is very flat (pancake) and so any mechanical metering system will suffer inaccuracies. When mine gets below about 1/4 on the gage the sending unit float gets "stuck" on the bottom until I hit a really big wave. It usually gets unstuck automatically, but if not, I can loosen the screws at the top of the sending unit, shake it around, re-tighten and fill the tank. Not a big problem for me since I usually keep my tank 3/4 full at least during hurricane season. Good luck.
 
Chuck, I don't have a 25 but I did have a similar smell. Bear with me for a moment. My original (plastic) tank had a bronze fitting "plastic welded" into the tank and into that was threaded a brass fuel fitting which attached to the fuel hose. Whoever tightened the fuel fitting into the tank fitting did it with enough force to split the bronze fitting, ultimately resulting in a noticeable leak. (photos in my album.) C-Dory immediately sent me new tanks, but upon closer examination after removal, I found the vent fitting on the old tank was also split! No wonder I always smelled gas whenever I removed the mooring cover.

The mothership has since switched tank manufacturers to Moeller tanks and the smell is gone now, but I'm sure you have the same potential for a split in the vent fitting arrangement at the tank even though it's aluminum. Even seeing the split is difficult though you may see a stain if you're a regular user of Stabil like I am.

I'm hoping for your sake that it's a hose problem. Replacing your tank would be a far more difficult project.

Don
 
The tank on my CD-25 is aluminum. I checked the connection on top of the tank and they are ok. I also drilled a hole in the fiberglass like Steve from Dora-Jean had mentioned and no odor there. I covered the vent and I think the smell is gone.....I'm hyperventilating...sniff...sniff
The fuel sending unit on top of the tank has 2 electrical connections. One is bolted an the other is a push on sta-con connector that seems a bit lose.
So I guess I'm still looking to make sure all is OK.....Keep the suggestions coming, they really help.
 
I have come to the point of putting fuel flow guages on my boats. Navman/(rebranded as Standard Horizon) has a unit for about $150. This reads total fuel used or gal/hr. Accuracy is very good. Also Lowrance has a new unit--in about the same price range using the MNEA 2000 bus system--and can also give miles per gallon.

Not only do these systems give a very accurate amount of fuel used, but show what trim and speeds are most effeciency. Doesn't take long at current fuel prices (over $4.00 on the water in some places) to make up for the cost of a guage and system.
 
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