help picking the right prop

[Big Kahuna]

when the go into the water tail first, the throttle is not pinned, in fact there is barley any gas being given, once your feet hit the gas, then it starts to accelerate and get the launch needed, but it is a pricise timed move, you ever see sometimes where they dont launch and just end up sitting on the hood, that sometime happens becuase the ski prop starts cavatating and not giving them the punch they need or they missed the throttle.

 

[DAG]

so getting sligtly off topic.. what Exactly is cavatation?



i can not pull out of a tail stand at all... i half to cut my engine and wait till the ski flat/surfaced.. and jump back on... there is deff somehting wrong... maby i got the wrong name for it...

 

[Big Kahuna]

A prop works by pushing water , it is low pressure in front of the prop and high pressure behind it, the reduction nozzle helps to creat the higher pressure after the prop creating thrust............. Cavitation occurs for 2 reasons........ One, air is getting passed through the pump disturbing the flow, or when the conditions are correct the prop looses its grab on the water in effect punching a hole in the water. If your pump seal is messed up it can let air into the the pump cavity causing the prop to loose its grip.........

someone may have a better discription..........

Side note, with Submarines, if they increase power to quickly or go say full reverse they will get cavitation...... Some people refer to this as boiling the water around the blades when this happens, wont go there!

 

[douglee25]

The easiest way to describe cavitation is pulling a vacuum on the water so much so that is physically seperates and actually boils.

Doug

 

[Big Kahuna]

there was a huge discussion on this last year about the fact of whether it actually boiled or not............

 

[douglee25]

By definition, the water vaporizes and forms bubbles of gas. I would think that means that it boils. No?

Doug

 

[DAG]

If your pump seal is messed up it can let air into the the pump cavity causing the prop to loose its grip.........

so here's my seal.. if this is the corerct one... think thats the problem...???

 

[Speedfreak]

I only have a stock bore and stroke motor. And my pump seal looks exactally like that. With the little folds on the edge. I do my jumps from a tail stand (just learning) the 2nd half of the 50-50. But from a tail stand at idle or close to idle you can hold it WOT and the ski will compeltly leave the water. Not by much just a few inches but the ride plate leaves the water.

I do have front exhaust and that might be what your problem is. Does the ski do it when you idle on your knees and you peg it WOT. If not then it sounds like an exhaust problem.

About blueprinting the pump you can search SBT's website they have a thread on pump blueprinting. It takes all of the casting flaws out of the pump area and makes for a better hookup.

 

[DAG]

Aww you say the S word....

allright thanks, i'll give that a try

 

[hangtime]

Bored nozzle + WW cone = cavitation 99% of the time

have one or the other

I must be the 1% because mine rips with my Skat Swirl on it and bored nozzle with cone :biggthumpup:

 

[2nd nature]

If you want a stock cone I would trade you my stock cone and cash for your ww cone.

i wouldnt pay for a wetwolf cone i had 2 and didnt notice sold and put stocker back on