Need help: Speed is down 3 mph even though it is colder out

[UTClason]

I was hitting 71-72 mph in 100 degree Texas heat, but now that the air and water temp are lower I'm only hitting 68.6 mph. I was feeling a vibration at 7200+ rpms that went away on its own (I immediately stopped and couldn't find anything in the pump). When I started back up, the vibration went away after about 2 minutes but my top speed was still only 68.6 mph at 8100 rpm.

When I got home, I pulled the pump and did not find anything really out of the ordinary. The impeller doesn't have a scratch on it, but the wear ring looks pretty worn (45 hours of use).

I've sent Richard an e-mail for these parts in addition to the mandatory upgrades (Riva Pro block-offs and Sponsons) that happen every time I touch a wrench and my ski at the same time. Besides replacing the wear ring and pump seal, does anyone have any suggestions on what I should look for to get my 3 mph back?

Ski/Run Info:

2005 RXP
Riva Stage 1 w/ the wedge
Riva BOV
Riva Finger Throttle Kit
Garmin Map 76CS
Air Temp 86 Degrees
Water Temp 73 Degrees
3 Bars of Fuel

[Jeff C]

Bad wear ring could scrub 3 mph off by itself. Start there and see if oyu get it back

[psycho rxp]

impeller blade could be slightly bent, causing lack of performance, oil level too high, or bad gas . 8100 rpm dosen't sound right if wear ring, or prop bent. double check the rpms.

[UTClason]

RPMs at WOT were between 8000 and 8100 depending on VTS and body position. The tach showed the same range when I was running 70+ in the Summer. This is why I am confused, usually if I get above 8000 on the tach I have no problem breaking 70 on flat water.

Oil level is unchanged since the last time and the impeller blades look ok (doesn't look like they hit anything). I haven't re-pitched (or touched anything else) since the 70+ runs either.

[psycho rxp]

possibly the difference between a full tank and 1 or 2 bars or gas

[UTClason]

Fuel level was 3 bars when I could only hit 68.6.

What else can affect top speed without a drop in RPMs? I can't seem to find a good answer for this: Can a wear ring wear out (affect top end) without cutting RPMs?

[Green Hulk]

Your wear ring is bad!

[jack]

Would a bad wear ring cause the vibration? That part sounds more like an impellor blade bent a little bit.

[Green Hulk]

I was feeling a vibration at 7200+ rpms that went away on its own (I immediately stopped and couldn't find anything in the pump). When I started back up, the vibration went away after about 2 minutes but my top speed was still only 68.6 mph at 8100 rpm.

Sounds like he sucked something up damaging the wear ring. He finally blew it out and the vibration went away.

Nevertheless, the prop should be inspected for a "kicked out" blade when you change the wear ring.

[Sundance]

UTClason---Strange you bring this up. I am having the exact same proplem--except mine dropped from 73mph at 8150 rpm to 68-69 mph at 8150 rpm. I have struggled with this for six weeks--inspecting--measuring--new wear ring--etc. and still cant find the ghost. I have an appointmet with PPG the week of Dec. 5th to solve this. Its a 14 hundred mile tow one way---but did this last January for their level one kit and Frazier's prop magic. I am extreamly staisfied with their work and knowledge. After a full summer of hard riding--someting has gone astray.
PPG will find it and I will post the findings and results. After they find it they will install the new upgraded racing ECU and some pump mods which should make it a consistant 75mph boat.