2002 gtx di speed improvement

[jimmyluke]

So my ski basically had two issues- one only running 6500 RPMs and number two only reaching 40 mph. My compression is 125 psi. I did not check fuel pressure this season, last season I had 105 or106psi? My raves are cleaned and I put a new O-ring kit in them last season. My water control valve has a new Bellows in it last season and seems to be working like it’s supposed to on the bench. One little note about that is the orifice under the water control valve has a 3 mm ID and according to the manual it supposed to have a 4 mm ID. I have another thread on that issue and was recommended to not drill it out- so I’ll let it go for now. I also put a new aftermarket wear ring in it last season and my clearances ranged from .012”-.024”. So for some reason I decided to check the run-out on my driveshaft and spec is .020” max and I had .120”! I thought maybe this is possibly affecting my knock sensor and possibly cavitation in the carbon ring/seal area. So I straightened it out to .002”. I had the new carbon ring/seal on hand but decided to only try one thing at a time to pinpoint what improved performance if any. So anyway I took it on the water and I had high hopes for some improvement but unfortunately straightening the driveshaft did not help performance at all. While I was on the water after getting no performance increase I took the rear seat off and the PTO cover and watched it as I was riding and did not see any water coming in at the carbon ring area. So I changed the carbon ring/seal with a new heavy duty one, and also raised my OPAS steering paddles all the way except for about 1/16 of an inch by using 5/8” shaft collars. I water tested it and got 50 mph and 6600 RPM[emoji3]. So a big breakthrough for me. I’m not sure which it was that increased my speed may be a combination of both and I won’t find out till next year because riding season is over for this year. I might drop the opas paddles back down just for testing purposes next year but I know I’m not gonna keep them down because I definitely like the way it handles better. They probably weren’t raising like they were supposed to because you could be going along and just out of the blue the ski would dart one way or the other unexpectedly and I did not like that. So I do have one question and that is could a carbon ring/seal be not leaking water and still cause cavitation? Here are two pictures of my old top hat and a side view of the old v.s new heavy duty.
Thanks Jim

 

[jimmyluke]

A little funny note on straightening the driveshaft. When I had the engine out of my other ski a 2001 GTXDI I decided to check the driveshaft run-out before putting it back in and it was.004”- well within spec. But I decided to “ tune it in“ anyway. so I put the ends of the driveshaft on blocks of wood and gave it a couple of wacks with a 4 pound dead blow hammer. Put it back on v-blocks and indicated .168”! It bent easier than I had anticipated. I eventually got it straightened out to .0015”. So when I straightened the driveshaft on my 02GTXDI I used a 3 pound dead blow hammer and needless to say a little less horsepower[emoji1].
JIM.

 

[mikidymac]

Your old stainless ring looks really bad.

When they leak air it will be like a clutch slipping. THe rpm's will be high but your top speed will be low.