Hi all its me again can anyone give me any idea where's best to locate the reed, plus my speedo came with 6 tiny magnets do I need to use them or would the bolts on the prop suffice.( I have seen a couple of cars with a toothed gear fitted between the prop and diff but cant find any for sale ) any help for a confused old man would be appreciated.

The magnet sticks reasonably well to the prop of its own accord and then I used a dab of jb weld to glue it there (incidentally i did it with sikaflex first and it flew off at speed but the jb weld seems to be ok). Close to the diff is best as your gearbox probably moves side to side significantly under power and makes it hard to position the reed switch close to the magnet without the magnet(s) hitting it.

You can't use the prop bolts as you need the magnet to operate the reed switch. When fitting magnets it is absolutely essential to make sure the surface they are going on to is spotlessly clean b4 fitting. use, meths or similar to degrease b4 fitting & use JB weld, araldite or similar powerful epoxy adhesive.