Laid Back Boaters

I finaly managed to get out to the Sac River today for a few hours with a buddy, and made a few videos. I'll post them in this thread as soon as they finish uploading to Youtube. Something I did notice today, is that I am getting a little cavitaion on a hard acceleration take off. you can hear it in the videos titled nozzle down takeoff & nozzle up take off. I made a video of nozzle down driveby & nozzle up driveby. Then one of flat out in the boat. in center position the boat goes the fastest around 57 mph by my speedo, you can feel the boat slow when you put the nozzle all the way down, but it cuts rough water much better, it almost wants to porpous at top speed all the way down. the only difference between center position and all the way up seems to be speedo indication. and it only looses about 3 mph by my speedo. I still have not played with the ride plate at all. It feels like I need to spend a bit of time experimenting with different ride plate settings, etc. Still need to find out what is causing the cavitaion (sounds like a berkley ) on hard acceleration dead start. Videos should be up shortly.

I also made a couple vids at the pump, to show what is going on back there, I'll post those as well.

OK, heres a video driveby with the nozzle all the way down

Heres a video driveby with the nozzle all the way up.

Heres a video of a flat out run in the boat, nozzle in the center, mostly

heres a video on hard acceleration from dead stop nozzle down & nozzle up.

OK, thats enough for today, I'm gonna go out on a limb here, and say "the rooster is way different than stock"

just a little It looks real good Steve! Did the pump cavitate with the diverter straight out?

Steve nice done videos.If I remember right didnt it when you and I tryed it have more down nossle to it .It looked a higher this time I think. And one more thing Have you had someone look over to back to see what is splitting part of the stream comming out the back ,just wondering what makes it do that. Sure looked great

The split tail is caused by the steering fin in the middle of the nozzle. I have a couple of vids taken at the pump while driving also. I'll upload those a little later.


Yup! Im still meditating on it. Its definately doing something in the way of cavitation, Its just like a slipping clutch. I was doing a little exit housing comparison (dimension wise) the stock exit is 3 3/8" X 3 3/8", and the Panthervater tube is 3 1/2" X 3 1/2" not enough to cause the issue I dont think. I will check the pump out more thoroughly to see if anything has appeared.

Heres a video of the pump while running through different positions with my modified panthervator. Im gonna pop it back off & check the rear bushing. looks like it has quite a bit of water shooting out the stator vent holes while under acceleration. I must admit, the twin tail is pretty unique!


Tell me what you think!

another cool video! it's pretty interesting at how much water is still coming forward. I wonder if a longer ride plate would eliminate a lot of that? The issue is a longer ride plate will divert the water flow directly to the transom when the pump is in reverse which is counter productive in trying to back up, I know that one from experience. The other thing I've wondered about is tapping the vent holes and plugging them off with a screw. Before doing that, it would probably be a good idea to install a couple of pressure gauges to see what's going on back there for a before and after test.
The cavitation thing is still a question mark. You said it wasn't cavitating at all prior to the addition of the diverter?
I'm wondering if it's really cavitation and not just the shape of the impeller blades being able to move the water in a more efficient way? If that's the case, it could be that it's causing more turbulence within the pump which has changed the pressure which could also explain the additional water coming out of the vents? That leads me back to adding pressure gauges to find out what the pressure is on the suction side of the impeller on a completely stock pump as opposed to yours and others that have been modified. I would imagine that the pressure would need to be the same as a stock pump which just reminded me of something else.
If that pressure on the suction side is too low, it can cause the water to vaporize. When vaporized, that gas can now be compressed which will cause a loss of efficiency.
For a simple test, pull the impeller, paint it, reinstall and go use it for a couple of hours. Pull it apart again to see if the paint is worn/burnt away, that will be a good indication of cavitation.

Kind of a lot to swallow

here are a couple of pretty cool videos showing cavitation on a propeller. Being the Panthers are using more of a propeller in a tube, this could be what is happening inside-

interesting thoughts cas, I think I'll tap a couple of 1/8" pipe thread holes in the pump, throw my stock exit back on it and see what kind of pressure readings I get before the impeller and in the exit housing. I have the exit housing removed and dont see any significant differences in the slipcote I painted on the inside of the pump. Then swap out the housings and see what readings I get there. I still see a considerable gap between the nozzle and housing as well, I may try and weld another small bead on the nozzle to tighten that up a little more as well.

Steve,
It's actually best to put 2 pressure gauges on the suction housing, one at about "10 or 2 o'clock" and the other at about "5 or 7 o'clock". The reason being is you will be able to see if the pressure is the same top and bottom to make sure the impeller is fully loading. The taps should be as close to the impeller as possible, in your case, as close to the front of the wear ring as possible. This is also where it's difficult with the Panther, there's not much you can do (easily) to change the intake side. With the Berk styles, that pressure is changed by changing loaders for the top side or adding a shoe to change the bottom.
A lot of people have put the gauge at the "9 or 3 o'clock" position but that will only tell you the median pressure which can help but it's not as accurate as top and bottom. Here are a couple of quotes from when we discussed this topic back on the original Laid Back board, unfortunately, they refer to a Berk pump but the same will apply to Panthers although the pressure readings are different-

here's a quote from ttmott -


and another by Timinator-