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11-13-2005, 10:23 PM #1
- Join Date
- May 2005
- Posts
- 4
Need help: Speed is down 3 mph even though it is colder out
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
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11-13-2005, 10:59 PM #2
Bad wear ring could scrub 3 mph off by itself. Start there and see if oyu get it back
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11-13-2005, 11:46 PM #3
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.
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11-13-2005, 11:55 PM #4
- Join Date
- May 2005
- Posts
- 4
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.
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11-14-2005, 12:10 AM #5
possibly the difference between a full tank and 1 or 2 bars or gas
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11-14-2005, 12:50 AM #6
- Join Date
- May 2005
- Posts
- 4
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?
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11-14-2005, 07:55 AM #7
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11-14-2005, 08:26 AM #8
Would a bad wear ring cause the vibration? That part sounds more like an impellor blade bent a little bit.
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11-14-2005, 09:14 AM #9
Re: Need help: Speed is down 3 mph even though it is colder
Originally Posted by UTClason
Nevertheless, the prop should be inspected for a "kicked out" blade when you change the wear ring.
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11-14-2005, 01:20 PM #10
- Join Date
- Jul 2005
- Location
- Lake Dunlap, Texas
- Posts
- 1,618
- +1
- 43
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.
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