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Re: Drive shaft with single uni joint

Posted: 17 Dec 2015, 10:49
by The Spook

The mounting of the engine and box together is a very good way to do it all, and yes it does leave the engine at the same angle as the prop shaft. I went down that track with my first hydro and it was a good set up. When I did mine I did make one mistake and that was that we assumed the piece of spline we welded into the drive setup on the crankshaft was concentric, it wasn't and this caused a mild vibration. On a later one we set up a center spigot in the lathe and used this to center the spline and machine the outer circumference of the drive spline to be concentric.

With the new one, because the boat is longer it gave me some more room length wise so I used a slightly shallower prop shaft angle ( six and 3/4 degrees down from seven in the old boat) and left a distance of about 12 inches between the gearbox and engine and I was able to flatten out the engine a bit. The resulting jack shaft takes up approximately three degrees of difference between the prop shaft and engine, with about half of that in each uni. This is called a "W" configuration universal setup. This setup actually has the engine further back than what Ted Jones specifies, and the C of G is 9 3/4 inches behind the sponsons when Jones specifies a maximum of 4". Graham Howard said 6" to 8" would be good. However the boat goes really well with the current C of G.