Fuel sender / gauge

[Tomsdad]

So gradually working through some issues on this new to me boat. Fuel gauge ( smiths gauge) only reads below half even though tank brimming full.
First cleaned connectors - no difference
Removed sender unit- this is 50 years old corroded and float full of petrol. It’s a smiths industries sender unit 3 terminals and six mounting bolts. So cleaned it up and drained and re sealed float. But now doesn’t work at all. So long and short need a new one. Research has said that sender unit and gauge need to be matched in the ohms range? But if they are both smiths industries should be ok??
So pics of original before and after cleaning and of one I have found online that looks very similar.
If anyone has been round this loop your thoughts will be appreciated.

 

[fredrussell]

As you say, the ohms must match. Is there a tech spec on the replacement sender advert? Have you tried putting a multimeter on sender outputs and measuring resistance as float rises? Just to check it’s not the gauge that’s faulty.

 

[Tomsdad]

I have contacted the manufacturer for this. I have also read that smiths fuel gauge works on 10 volts so there should be a voltage regulator somewhere ??

 

[vyv_cox]

I replaced my ancient float and arm type with an Osculati cylindrical type. It has proved totally reliable. European boat, so resistance matched. Story here Sadler 34 fuel tank