Need help diagnosing...

05 RXT with 8 hours.
With Riva Stg II I was running 7900rpm at 2200 elevation.
Boat ran strong with no issues when previously ran.

Ran at same lake and could only get to 7350rpm and then dropped to 7250rpm max. Checked engine temp etc. and all was good. Checked to see if I sucked anything into pump and all ok...prop ok...wear ring ok.
Pulls ok out of the hole but will not rev out like it used to the previous ride. I did not change anything from the previous ride except fill ride plate holes and match grate to hull. At the lake, I pulled the intake hose off to check SC impeller and could not slip by hand. Checked plugs and all OK visually. Oil level ok. Ran 1 tank of gas through and nothing changed excpet for slight loss in rpm which was probably heat soak as I have not installed the thermostat yet.

Took to dealer and checked on computer. The only thing that came up was throttle position sensor slightly off. We checked throttle stop and reset sensor on computer. We also checked to make sure knock sensor was plugged in good as well...ok.

Would the TPS sensor be enough to make me drop 500-700rpm? It was not off by much. Maybe 1-2% tops. Definitely seems to be engine related vs. prop-pump issue. Maybe bad plugs although they tested ok on the computer. Will replace anyway to make sure not bad under load. Will reseal IC plug although I sealed well when installed not long ago. Have heard of issues with slipping SC but at 8 hours?

Anyone have any ideas as to what might be the issue?

No one?

XenonX: Try the soapy water test. With the motor running, spray all the hose connections with the soapy water and rev the ski to see if there are any leaks by the couplers. Stupid, but works! Be sure to spray the exhaust hoses as well. My i/c couplers have slid off the i/c several times over the last few months; especially on the underside of the pipes where it is hard to see. The hoses might look like they're on, but are actually off!

No cavitation at all?????

Brendan

'04 RXP STG III w/B kit s/c 81.0 (80.5 MB II 2006)
'02 XP - (stock 61.9)
'01 GPR 1200 IR STGII (76.5)

http://www.windmillhotdogs.com/

This message has been edited. Last edited by: BDNJ,

Brendan,

I did not see your post until now. Just thought I would let you and others know that you are exactly right. My low rpm issue was caused by the Riva Inter Cooler slipping back and pulling the coupler just enough. I could not see it from the top but there was a gap at the bottom.

I did not figure this out until I ran the engine and felt air when getting on the throttle. I checked all of the connections and it was the connection coming off the SC. I felt pretty stupid as it wan an easy fix and could have been done at the lake.

All taken care of and now my RXT Riva Stage II just ran 8100RPM at 800' elevation without pump wedge.

I don't know about the RXPs but the RXT handles like crap with the pump wedge. For those who only drag race maybe, but I like to carve my turns.

Hey- glad to hear you got it all sorted.

Brendan


'04 RXP STG III w/B kit 81.8 (80.5 MB II 2006)
'02 XP - (stock 61.9)
'01 GPR 1200 IR STGII (76.5)

http://www.windmillhotdogs.com/

quote:

Originally posted by XenonX:
Brendan,

I did not see your post until now. Just thought I would let you and others know that you are exactly right. My low rpm issue was caused by the Riva Inter Cooler slipping back and pulling the coupler just enough. I could not see it from the top but there was a gap at the bottom.

This same thing happened to my stage II RXT a few times in the past but not anymore, just put some high temp silicone between the couplers and the IC plastic tubes and let them cure for 24 hours, this should solve this issue

Ray

Ray: The RR motor mount really tightens things up; worth it's weight in gold!



'04 RXP STG III w/B kit 81.8 (80.5 MB II 2006)
'02 XP - (stock 61.9)
'01 GPR 1200 IR STGII (76.5)

http://www.windmillhotdogs.com/

[QUOTE]Originally posted by BDNJ:
Ray: The RR motor mount really tightens things up; worth it's weight in gold!
/QUOTE]

Hi Brendan, this would be my next mod then, thanks

Ray

quote:

Originally posted by Gpr/STX-15F/RXT:
[QUOTE]Originally posted by BDNJ:
Ray: The RR motor mount really tightens things up; worth it's weight in gold!
/QUOTE]

Hi Brendan, this would be my next mod then, thanks

Ray

Good idea Ray. BTW - 74+ on a T!!!! Awesome numbers!


'04 RXP STG III w/B kit 81.8 (80.5 MB II 2006)
'02 XP - (stock 61.9)
'01 GPR 1200 IR STGII (76.5)

http://www.windmillhotdogs.com/

quote:

Originally posted by BDNJ:

Good idea Ray. BTW - 74+ on a T!!!! Awesome numbers!

Thanks Brendan, by the way yesterday i rode my ski again and ran the same speed as last week (74.2)

Ray

That's great Ray. I'm 81+ everytime I go out. And it's 90 degrees everyday up here now. Plan to test the skegs this wknd and then I'm going to pull the nose cone and see what type of gains I get.

I'm now looking for 82+!


'04 RXP STG III w/B kit 81.8 (80.5 MB II 2006)
'02 XP - (stock 61.9)
'01 GPR 1200 IR STGII (76.5)

http://www.windmillhotdogs.com/