Seadoo prop pitch recommendations

[ScreaminXP]

I have a 97 xp with an SBT block with 16 hrs on it. The stock prop is on there (16/23) and I am thinking of replacing it. It has an 85/88 nozzle and a new wear ring, but I have had cavitation on takeoff ever since I added a Rossier ECWI pipe and R+D rec head. It has been doing the cavitation thing since before the new engine as well, since the mods. (even on the old engine)
Even with the new wear ring, the outer edge seems a bit more than it should be between the edge of the prop and the ring. The most RPM it ever can turn is 6730-6750, but I get near 60 mph average on GPS. I ride where it's smooth water for the most part and want to spin slightly more rpms to get my pipe up into the range where it makes a little more power. I expected more rpms with this setup and flame arrestors, carbs rejetted, chokes removed, new rotary valve, etc. The old one did the same thing..low rpms. Shouldn't I get 6900-ish?
The low end takeoff is fine (as soon as it "hits" and the cavitation stops) so I'm looking for mainly more speed on the top end. The pump is sealed and double sealed again, but it still does it, and the prop looks in perfect shape and I'm careful never to run in shallow or suck anything in there so the cavitation remains a mystery.
Hoping the prop can help out, what would anyone recommend for a replacement? I do realize different brands measure them differently to each other and to the stock pitch, but what I want is a bit more on top and to hopefully ged rid of the cavitation.
If I go less pitch, in theory, won't that allow more rpms, which could mean more top end speed,(or break even) even though the pitch is less? (and also aid in reducing the cavitation)?
Any recommendations would be appreciated.
Solas X1(?)

[ February 12, 2002, 06:55 PM: Message edited by: ScreaminXP ]

[ScreaminXP]

I also have tweaked the mixtures to optimal settings and made sure the EWCI is shutting off completely at top speed. I reduced the size of the water jet on the midsection of the pipe and increased the stinger flow jet and got about 75-100 rpm more. I also have a 65 jet trickling water into the waterbox as a safety so I don't burn the rear hose in case one of the front waterjets clogs up or it runs too hot on the exhaust. I tried piching off that flow, and it made no difference in rpm, but the rubber pipe ran a little hotter, thats it. Squish clearance on the new engine was .060 (!?) and it's now .040 and cranking compression is 155 on a gage with a schrader valve in the hose. The old engine was showing 160 on the same gauge with the same head. (when it was alive)before the crank bearings died.
I really think my prop/pump isn't reaching full efficiency because of the bypass the clearance is allowing (its about .030 except in one area where it just about touches the ring) but it revs and cavitates until theres enough forward movement for the grate to feed the pump..then its like revving a car and dumping it into drive from neutral at 2000 rpm.
As long as its moving, even at low speeds, its fine. As soon as you come to a complete stop, it will cavitate on the initial takeoff. Its got an aquavien intake grate if that matters.
You can hear a low rumble when it does it, and the engine acts like its revving so high its hitting the rev limiter, but my junk digital tach doesnt react quick enough to tell me if thats the case. Any ideas? It is in perfect condition other than that one thing, and with a fresh engine, I plan to keep it awhile so I want to get the most out of it and fix the prop thing now during the cold water season.
THX

[ February 12, 2002, 07:16 PM: Message edited by: ScreaminXP ]

[Bill O'Neal]

ScreaminXP,
Although you have sealed the pump to the pump support, you may have a very common problem on some of the 97 and 98 XP's that I have come across. The pump support plate may not be sealed well to the hull itself. When it is not sealed well enough, the motor will scream at high rpms, while the boat slowly accellerates until it gets a little forward movement and the water is jammed up the intake tract and into the impellor.
This would be my first guess as to what is happening to your boat.

Yes, putting in a lower pitched prop, or a swirl will help the accelleration, but until the pump plate is completely sealed, you will still cavitate. Once you have everthing sealed, you might want to try another impellor. You could send yours to Impros and have David re-pitch it, or you could buy another prop. I suggest a Skat Trak 15x24 slimline, or if you really want hookup more than speed, try a 16x23 swirl.

[ScreaminXP]

Ok, thanks. I did have to replace that pump shoe once, but I used "the right stuff" to seal it, and it was okay after that, but then developed the cavitation right after the mods. Maybe the seal broke down after that. I will rip it apart and reseal it to the hull when I do the prop job.
I do want more speed more than acceleration, so I assume the 15/24 is the roughly equal to the OEM 16/23? I want something new with a nice polished face to it. The stock one looks like a rough finish in a lot of areas. How would that prop effect my top end rpms? (if any)
Thanks again.

[ February 12, 2002, 08:19 PM: Message edited by: ScreaminXP ]

[Bill O'Neal]

ScreaminXP,
You really need a prop that works well with the powerband of the exhaust system. Talking to David at www.impros.com or Rick at Rossier may be the best advice I can give you, as I haven't used a Rossier pipe on anything I've built in 5 years or so.
An X1 is alot more impellor than you have now, and would lower your rpm. If using a Solas, it should be an XO, and when I use them with my FPP systems, I take some pitch out of them.