If they can't supply the parts then they do a new one at about £220 the part you want is 128170-77010 GM series starter motor. However, I picked up a new one on eBay for £75.
There's currently a new one going for £210 - eBay item 320214916053
The other alternative is to try getting the parts or a reconditioned starter from the USA. I recently got a reconditioned water pump for less than a third of the cost of a new one in the UK and that included shipping. Try this guy:
I bought a replacement starte last summer from the guy in Bellshill who sells starters and alternators on ebay. Here is another - ebay item no 150213018902 at much less than half the price from a Yanmar dealer. An auto electrician might be able to get you specific parts if that's too expensive.
[/ QUOTE ] I find mine very useful to give the engine a monthly turnover to circulate the oil while laid up but I have never managed to start her with the handle and I don't know of anyone who has.....