I had the same condition on my 2470, I replaced the sender, it was frozen, with a Tempo mechanical sender. They have one that is the same size as the was original. I don't recall the model or depth. The new sender had a sight gauge that I replaced with electric remote reading unit, also from tempo. This is compatable with Yamaha electronic gauge. All told about $ 100.00. Simple repair.
http://www.tempoproducts.com/2004/gauges.html