Help with fuel gauge

[loydt]

Hoping someone here has a similar problem. I have the Smartcraft system on mine and my fuel gauge only reads accurate when the key is in the on position. As soon as you start the engine, it will read almost empty and then while underway sometimes it will fall completely to empty and i get an alarm. Last year we replaced the sending unit thinking that was the problem. I calibrated everything again while at the gas dock like the book says but still doesn't read correctly.

Any ideas?

 

[Bt Doctur]

Check the tank ground to make sure its connected to the engine block ground
one lead to the neg battery post, other lead to engine 0 ohms
next move lead to tank, 0 ohms
If the tank is plastic, test to the flange
When all else fails , install a analog gauge

 

[Sharritan]

I have had the same issue for years with my 185 Sport. I replaced the sending unit 3 times, replaced the gauge, checked the polarity, etc.... My issue is that the gauge reads fine from a full tank to 1/2 full, then it reads empty. Then around 1/2 tank it reads accurate again. My best guess is it has to do with the shape of the tank. Fortunately on the 185, I can lift my sundeck and actually see the tank, so I can see the fuel level. The tank shape is odd, and it has a "shelf" like layout where the top of the tank is a lot wider than the bottom. So, my assumption is that the transducer gets thrown off when the tank is between 3/4 and 1/2 full.

I know this doesn't help you, but I figured I would share since I posted this issue no less than 5 times a few years back, and was never able to correct it. As I mentioned though, in my case it really isn't a big deal since I can see my tank so I don't have to worry about being surprised by running out of fuel. Hope you find the root cause.