Speedo help on 92 Griff please.

[vestas]

My speedo started playing up a couple of months ago by bouncing 10 mph each way constantly. I decided to leave it until service time but toady took her out and it wont go above 15 mph. I know there have been previous threads about similar issues but anyone know what to do on a 92 griff?
Thanks
Vestas

[mrmaggit]

Sounds like you need a new sender.