That'll definitely do it...

I remember years ago when i had an assortment of senders, all looked exactly the same, but the internal resistance that controls the output to the gauge varied so much, i could go from nothing on the gauge, to normal, to off the top by testing it with the different sensors.

I suspect if you are absolutely certain it is running at the right temp, then you could use a small trimmer pot wired in series, and trim it down to the normal region instead of buying a new sender...