Yes, forget the fuel gauge and start using engine hours to figure the fuel use. Our M25 uses less than a half a gallon an hour for the past 11 years. Larger engines use a bit more. The tanks aren't symmetrical so half is really less than...

Well we are all different as I do not agree with not using a fuel gauge. It is there for a reason and I do not know of many boats that do not have none. The one you have may not be the best. There are non mechanical ones with no moving parts out there now that are very accurate. We switched to one over 6 yrs ago and love it. It takes a bit of setting up bit never have had 1 issue with it.

Randy

It all depend on what you depend on! Really. I know that there are now newer gauges that don't require the mechanical arms and the sliding scales that always used to break. It would be helpful to know what you installed that works so well.

They put fuel gauges on boats because they're easier for people to understand. That doesn't make them right, because a majority of fuel tanks we've seen have been NON rectangular in shape, so if they're narrower in the bottom and the gauge is linear, there's a LOT less fuel left than what the gauge says when it read 1/2 or 1/4. We have a 23 gallon tank. I usually get it refilled when it's half empty, so about ten gallons. So I fill up every 20 engine hours, and simply keep good records. I find it easier to use than a questionable fuel gauge, don't have to spend $$ for expensive gauges or for a series of cheaper ones that I'd have to replace every few years. My boat, my choice, but this is just another different way for people to address the poorly designed "standard" fuel gauge mechanisms that were installed on our tanks; the gauges are fine the tank sender is the culprit.

Klaus,

If you are sure the gauge and the sender are ok, you have a wiring problem. I do not recall which way our system are set up but, assuming the fuel gauge system is getting power, if you short the lead the gauge will
go full deflection one way when you pull the lead off and have an open circuit the gauge will read full deflection the oposite way. Again I forget what way the needle will go but. my guess you either have a shorted wire or an open wire in your circuit.

As for the tank in the C36, the standard tank is a rectangle with square sides and the quantity should be completely linear, often the level sender is not linear but should be its most accuarate at the empty or east reading.

As asked about, Here is what I installed that is a non mechanical fuel sender unit. No sliding parts either. Works off ohm resistance

[url]http://www.livorsi.com/catalog/senders.htm#fuel_level[/url]

13-24" GSFLC24ATL $96

Catalina direct offers the regular fuel sender unit for $35

[url]http://catalinadirect.com/index.cfm?fuseaction=product.display&Product_I...

Randy

Klaus,

I was unclear about the trouble shooting. To trouble shoot the system discontect the lead from the fuel quantity transmitter. If you have a complete circuit you will get full deflection one way with the lead disconected, it you touch this lead to ground you should get full deflection in the oposite direction. There will also be a ground lead at the transmitter or on the tank next to it, make sure that circuit has a good connection at the tank and that it has continuity to the gauge. The level sensor is just a variable resister who's resistance changes based on the angle of the arm on the float, o resistance gives full scale one direction infinite resistance reads full scale in the oposite direction, resistances in between give you indications in between.

I took another approach when my fuel tank gauge died 2 months ago. Since the accuracy of the fuel tank gauge system is not very good (at all) I installed a sounding valve/tube. I removed the float gauge assembly from the screwed on cap on the tanktop, drilled a 13mm hole in the cap and installed a small 1/4" ball valve with a suitable fitting into the hole, and re-installed the cap plate. The 1/4" ball valve sticks up less than 2 inch above the fuel tanktop and does not interfere with the seat board. This gives me an easily accessible sounding tube that I can open and close. I made two sounding rods, one is a 3/16" brass rod with a small groove carved in with my Dremel tool at each gallon level (at 12.5mm intervals), the second is a 3/16" wooden dowel with paint marks at every 5 gallons (62.5mm apart). The brass one is most accurate but it is a bit hard to see the fuel level on the brass rod. Anyway, it is very accurate, so now I know exactly how much I can fill up w/o overflowing fuel through the vent. I have some pictures if someone is interested in this.

Hans Treu
Dutch Boy, Hull 849

Option (Steve's hairbrained idea)#47 For those who realy want to know their tank level.

Dayton Grainger has drum gauges available for reading the level of fluid in a 55 gallon drum on it side. A 55 gallon drum top is just a bit taller than our tanks. The gauge is a simple heavy wall glass tube in a plated steel body. I believe it would fit nicely under the sink bolted to the inside of the cabinet. If teed into the outlet of the tank at its bottom and teed to the vent at top and mounted even with the tank, it would give a site gauge for the tank. No moving parts, no wires just a direct view of the fluid level. They are compatable with diesel are dirt simple, it would also give a clue to how funky your fuel was in the tank.

Other site gauges are available that could be used for water or waste level, though simple clear plastic hose installed the same way would do the trick for our non-flamable fluids.

I may put this on the list if, I ever find the bottom of my list.

A idea that has rattled around in my brain for several years, but never been acted upon, is to drill three or four 3/4 inch diameter holes though the wood partition that separates the aft cabin from the fuel tank bay. The holes would be aligned vertically, about 4 inches apart, and would allow a flashlight to be shone through one of the holes into the fuel bay to (hopefully) allow a viewer to see the fuel level in the tank. As Steve points out, this is a Mk II idea, as the fuel tank on this series is made of translucent plastic.

Is there any merit to this idea? What are the downsides, I wonder. Possibly diesel odor in the aft cabin, but that could be mitigated by cementing a plexiglas "lens" over the holes, on the inside of the partition.

Sometimes I really would like to absolutely positively know my fuel state. Usually, this is out of fear of a possibly overflow on filling. But it would be helpful also when prepping for a long distance ocean passage.

Larry,

I do not know the MKII boats at all. On the the MKI boats the tank is just forward of the sink under the seat and is aluminum. I would need a very powerful flash light to check my level.