RE: Kyosho Jetstrem O.S. .10
Are you referring to a Jetstream 800 GP? If so, I have the manual for the boat and found out that you can order parts for it directly from Kyosho - I was really surprised to learn that they still carry parts for this model. I was able to get a new set of motor gears for mine. I am guessing you are referring to the U-Joint at the stern which is between the hull and rudder -- if this is the U-joint you are talking about - which it should be since its the only one - it is a 4mm Universal Joint. Hope this helps - I would post the manual but it's 1.5MB... if you need it just let me know and I will e-mail it.