SXR 18/20 C75 Skat cavitating

Hirschfelt

Hirschfelt

Location
Buffalo, NY
Motor is set up for low end. At 839cc, running TL, ECWI, 100 octane and 48 novis. Originally it was a 15/20 C75 Skat. Now it is a 18/20 and still cavitating. Root pitch is 18. At the limits with getting much more out of the leading edge. Using a 82mm reduction nozzle and a stubby cone. Going to try and get a stock sxr reduction nozzle that should help and also use a stock cone. My only problem is that it seems backwards to want to try and slow down the prop with the smaller reduction nozzle and cone. It seems like it will hold back the potential of the motor. But if it cant load the pump/impeller properly the power is useless. Possibly a 145mm mag????

Thoughts / opinions?
 
Scorn800

Scorn800

Ride for life
Location
North NJ
Get rid of the stubby cone. They do not work well with steep pitch props. You need to load the pump more. Try a tbm cone.
Wants rpms you spinning?
 
Hirschfelt

Hirschfelt

Location
Buffalo, NY
6550 with to lean of a pilot jet. Replaced it and a world of difference. The wild part is that my carbs arent even dialed in yet and the prop is spining. Carb is close though. I think the builder said porting falls off at around 7500 rpm. I could be wrong. Have to check the notes. I dont want to buy the TBM as I feel the magnum pump is going to be needed.
 
Scorn800

Scorn800

Ride for life
Location
North NJ
Your rpm's are way off. Go back to the 15/20 with stock cone and nozzle.
You need to be atleast 7200-7300 or the boat is going to run like crap
 
Hirschfelt

Hirschfelt

Location
Buffalo, NY
Head gasket was leaking water into the rear cylinder. The ski seems like a hole new boat with the larger pilot in it. I couldnt do high rpm run yesterday due to the water leak. Pulling the head tonight to see if there is any damage. The cavitation is much less at 18/20 than it was at 15/20. I can hear the motor hit the rev limiter off the bottom. Getting a stock cone this weekend and have a 80mm reduction nozzle to put on. I think the sxi pro and sxr have a 78mm stock reduction nozzle. Should I get the 78mm nozzle? thx for the help
 
Proformance1

Proformance1

Liquid Insanity
Site Supporter
Vendor Account
Location
New York Crew
Could be. I should stop up and see exactly what you have, im just swamped here trying to get my SJ back together before its too cold to ride it. I want to make sure its good to go before Daytona. I just got rid of my spare. Can you borrow someones SXR ventrui for testing? No one is still riding except us crazys now anyway. If you are running a shortened tail cone, lose that also, but in steps so you can compare. Same there borrow an SXR one if you dont have it.
 
Hirschfelt

Hirschfelt

Location
Buffalo, NY
Proformance1 said:
Could be. I should stop up and see exactly what you have, im just swamped here trying to get my SJ back together before its too cold to ride it. I want to make sure its good to go before Daytona. I just got rid of my spare. Can you borrow someones SXR ventrui for testing? No one is still riding except us crazys now anyway. If you are running a shortened tail cone, lose that also, but in steps so you can compare. Same there borrow an SXR one if you dont have it.
Click to expand...

Not sure on borrowing a venturi? Should have one coming this week though. Should have the water leak issue figured out. Just have to put the head back on and waite 24 hrs for the copper spray to set. Justin should have his new concord in tuesday.
 
OCD Solutions

OCD Solutions

Original, Clean and Dependable Solutions
Location
Rentz, GA
I read a similar problem in another thread and thought the answer may offer up another possible solution for you since your issue does not seem to be typical.


Taken from this thread http://www.x-h2o.com/threads/17913-Idok-s-ski-s&highlight=Idok's+ski

SUPERTUNE said:
Idok,
I'm wondering if maybe the pump shaft tube had a small air leak in the Rev hull, as that will make a prop act smaller than it's pitched at.
You might go with a 12/18 Skat-Trak and a stock pumpcone with your bored nozzle, and check the pumpshaft tube for any airleak.
I use a A/C vacuum pump and a round disk with closed cell foam glued to it and a fitting to plug in the vacuum hose. Use waterproof grease to seal to the tube.
Note: Must always vacuum test pump shaft tubes before changing prop pitch!
Click to expand...
 
Hirschfelt

Hirschfelt

Location
Buffalo, NY
OCD Solutions said:
I read a similar problem in another thread and thought the answer may offer up another possible solution for you since your issue does not seem to be typical.


Taken from this thread http://www.x-h2o.com/threads/17913-Idok-s-ski-s&highlight=Idok's+ski
Click to expand...

outer shaft tube has been sealed up flush with 5200. Season is about over up here is a few weeks so I can check the engine side of the tube and reseal the hull bearing plate as well. The pump tunnel on my ski might be to small or insufficient for the amount of water the motor needs. I am using a 750 sx hull currently. I have been looking into a new hull. Q8 or BOB, but I know I need a 145mm mag pump and thats 2k. Waiting on my lotto #, J/K.

Need some clearification: the shaft tube will be full of water or mostly full of water at low rpms. The air leak will make the prop act/respond as the ski would be at higher speeds? less water intube while getting up on plain due to water entering tube from engine compartment?
 
Hirschfelt

Hirschfelt

Location
Buffalo, NY
Malone recommended the 145mm mag for the setup. He uses the 142mm mag with stock sxr: stock electrics, Factory pipe and some higher compression than stock to do backflips with the Q8. My goal is to get the Q8 next season or the season after. I am a bit hesitant on that large of a pump as well. Does seem big. But Malone knows kawi motors better than most and uses the 145mm mag on alot of his Q8 setups for a variety of power plants. Going to get it from him and follow his recommendations for the pump. Deff 142 or 145 set back.
 
CARBONX2

CARBONX2

Location
South Africa
Check seals and bearing on bearing plate, also check bearing plate for cracks in rubber on the back-side. Make sure driveshaft tube is properly sealed, that no resin has come off letting air through glass. I was also struggling with spinning props until I followed Chucky's advice from another thread, ski hooks up like a beast now
 
You must log in or register to reply here.
Top Bottom