C27 fuel gage problem

[Gordon S.]

My newly acquired '88 C27 shows a full tank of diesel on the gage continously. After 10 hours of motoring on the delivery trip. the gage still showed full. It is a 15 gallon tank supposedly.I have checked the sending unit with an ohm meter and it shows about 30 ohms with the tank about 90% full and I can see the resistance changing as the boat rocks at the mooring. So it appears good.At the gage end, when I short the gage it reads full. If I put a resistor box across the input I can make the gage register in steps down to empty as I add resistance. At 10000 ohms the gage reads near empty. The shape of the tank indicates that most of the fuel is in the top 1/2 so naturally the gage would be slow to show fuel usage from when the tank is full.I do not want to pull the sender in mid season as it looks like you can get into big trouble here and somehow one of the hold down nuts is already missing.Any ideas? Could the gage be faulty even though it seems to be working?Gordon S. C27 6529

 

[James]

C27 fuel guage

Gordon,If you are powered with a 1 or 2 cylinker diesel (i.e. Univeral 5411), you should know these motors consume about 1 quart of diesel per hour at mid range rpm. They are very fuel efficient. Ten hours of motoring might consume 2.5 to 3 gallons of diesel fuel. There might not be any significant indication of level drop in the tank at that point.Removing the sender from the tank is easy enough. Removal would be the quickest way to get peace of mind. Also, replace the fastener that missing.

 

[Gordon S.]

TNX James

Thanks for the reply. After my 10 hours of motoring at about 80% power I was able to add 5 gallons to the 15 gallon tank without overflow, but the gauge had never really moved from the pinned full position. I now suspect there is a shunt resistor in the gage that is gone open. Anyhow the fuel will be old before it ever gets burned. I'm not used to this kind of efficiency. My crew claims that the boat makes fuel when under sail.

 

[Steve W]

fuel gauge

Have Universal 14 hp FWC diesel in my 1986 Newport 28 MKII. had the same problem. Got tired of screwing around with it, bought a new gauge and sending unit kit for about $35.00 at West Marine, installed it in an hour and problems solved. Here's a neat tip when you install a new sending unit: use a gasket sealer to seal the sending unit gasket to the tank opening. Use no sealer on the top side of the gasket, then screw in the sending unit. This allows you to remove the sending unit for inspection or to pump out a few gallons of nasty fuel off the bottom of the tank, without messing up the gasket. This proceedure has never leaked for me. Good Luck.