DIESEL TANK GAUGE NOT WORKING - HOW MUCH DIESEL DO I HAVE?

Oct 8, 2023
32
Hunter 30 Lake Travis, Austin Texas
Stupid question, but I don't trust the fuel gauge on my 30' Cherubini as it has always registered 100% full since I've owned it for the last year. How do I verify the amount of diesel in the tank? I've probably run the engine no more than 10 hours.
 
Jan 1, 2006
7,355
Slickcraft 26 Sailfish
On my Ranger 29 the fuel tank was below the cockpit. I used a dowel pushed thru the fill opening to the bottom of the tank. Where it was wet was the amount of gas in the tank.
 
Sep 25, 2008
7,249
Alden 50 Sarasota, Florida
On my Ranger 29 the fuel tank was below the cockpit. I used a dowel pushed thru the fill opening to the bottom of the tank. Where it was wet was the amount of gas in the tank.
“Sticking the tank” is the typical method of determining the level. The tank dimensions will provide volume. Actual fuel amount can then be calculated. Therefore, you don‘t need to fill it up to find the answer. And with the engine's consumption spec, you then know how much run time you have.
 
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Oct 8, 2023
32
Hunter 30 Lake Travis, Austin Texas
“Sticking the tank” is the typical method of determining the level. The tank dimensions will provide volume. Actual fuel amount can then be calculated. Therefore, you don‘t need to fill it up to find the answer. And with the engine's consumption spec, you then know how much run time you have.
Thanks guys.....will do.
 
May 17, 2004
5,412
Beneteau Oceanis 37 Havre de Grace
Also listen to the fill tube as you add the diesel. The tone will change when fuel gets to the top of the tank. There are also custom made vent whistles to make the change more noticeable, but I’ve always just done it by ear. Once you’ve done that a couple times to measure engine hours vs gallons used you’ll be able to judge how much to take better than most gauges.
 
Oct 8, 2023
32
Hunter 30 Lake Travis, Austin Texas
I've verified I have a faulty fuel gauge. I'd like to replace the sending unit and fuel gauge together. Does anyone have a recommendation on which parts to buy?
 
Oct 6, 2007
1,084
Hunter H30 1982 Chicago IL
I replaced mine about ten or twelve years ago. Sorry, I don’t recall the brand and can’t get to the boat today, but I’m sure it came from West Marine. I may have just replaced the float type sender unit at the tank and not the gauge next to electrical panel.

I installed a fuel vent whistle about ten years ago and concluded that it’s really made for a boat with a much larger tank that’s filled with a wide open fuel pump nozzle. Seemed like good idea, but just made a big mess. The whistle makes no sound unless fuel is going in at a higher rate than my little twelve gallon tank can accept. So I learned the hard way that I need to fill my tank very slowly and just listen and watch closely.

If your tank is below the cockpit with the fuel fill offset 2 ft in the aft lazarette like it is on my ‘82 H30, then only way the get a stick in the tank is to pull the fill hose off the tank from the starboard lazarette. Extremely inconvenient and a good way to spill fuel into the bilge. Not something I would do.

Best to just replace the sender unit and gauge if you need to. When you have the sender unit out, you’ll be able to see how much fuel is in the tank and how clean it is. If you’re concerned it might be too full to remove the old sender unit without a spill, siphon or pump out a gallon or two through the fill hose to be safe.
 
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Oct 8, 2023
32
Hunter 30 Lake Travis, Austin Texas
Thanks Dalliance! I pulled the sending unit today and tested it. Very inconsistent ohm readings, so I ordered a new sending unit plus a matching fuel gauge from Amazon. I'll install it this weekend after testing it first.
 
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danm1

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Oct 5, 2013
190
Hunter 356 Mamaroneck, NY
Filling my tank is a two person job. It's a plastic tank and while someone pumps diesel I put a flashlight on the top of the tank. The level is clearly visible and I shout when it nears full...or I figure the fuel consumption based on experience (about 5/8th gallon per hour) and just add a bit less than I think it will take.
 
Oct 6, 2007
1,084
Hunter H30 1982 Chicago IL
Filling my tank is a two person job. It's a plastic tank and while someone pumps diesel I put a flashlight on the top of the tank. The level is clearly visible and I shout when it nears full...or I figure the fuel consumption based on experience (about 5/8th gallon per hour) and just add a bit less than I think it will take.
Two person operation for me too. I generally have a rough idea how much fuel I need, I have to dribble it in very slowly and my gauge display is next to the electrical panel where I can’t see it. On the rare occasion when I have crew, they can read it off from below. Usually though, I just ask the fuel dock attendant to stand at the pump and call out each gallon to me. Aluminum tank so the flashlight trick (clever idea) is not an option.
 
Oct 8, 2023
32
Hunter 30 Lake Travis, Austin Texas
Installed a new sending unit and fuel gauge I purchased from Amazon (links below). Works great! Now I have to fix/replace the hour meter.

Fyi, the sending unit varies based on the depth of the fuel tank. My tank needed an 8" length, but yours may be different.

Fuel gauge - Amazon.com
8" Sending unit - Amazon.com
 

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