Hi all, this may seem a bit half baked , but do you think I could use a couple of old jumper leads to use as a emergency ground by dangling the end in the drink ? the original through hull ground plate has been removed but the cable from the radio that was connected to it is still there . So I was thinking continue that on and over the side with the jumpers....?? What do you recon ?

You need area - the jumper leads won't be as effective as the sinterered bronze earth plate. You could do sheets of copper in the bilge that use impedance through to the water. Has to be large though.

I have always had best success with putting the tuner right under the antenna and then getting the longest run ( from stern to front keel bolt) of earth plate so on a defiance about 6 m long
usually use spark plug cable between tuner and antenna
HF is more art than science as they say