Alternatively find a siezed longshaft & buy the bits. (probably more hassle for you than turbo's suggestion).
At a guess you'll need the long version of leg, drive shaft, water tube & gear change rod.
Some older engines (from the 60s & 70s, a few crept into the 80s) used an insert / spacer at the bottom of the leg. With that you would need the spacer instead of the long leg casting. (which is an easier conversion, as you don't need to take all the clamp / swivel gubbins off, just drop the gearbox & replace the bits.)
I got a quote for an extension kit from the states, £280 shipped but not including import duty.
Price from Yamaha for a new leg, shaft, tube, gear shift and all the seals and gaskets - £200 to my door - much more work involved but cheaper and neater.
I could be way off the mark here (imagine!) but looking around this last while I've noticed that short 8hp Yammies are selling for a touch (£100-150?) more than their long shaft brothers...
Have you considered flogging yours, buying a long, trouser the difference and save the cost of the conversion? (potentially saving you £350)
Nice cheap one (granted, It's a Long Way to Tipperary)
