How to bore out a Pozi Nozzle on a Jet Drive

[mrtoybox]

I'm still working on the other planing issue I've posted.....but.....I've heard about boring out the nozzle because of my increased HP (350-400). Does just the round part of the nozzle that directs the stream need to be bored out? I notice there is a structure inside the Pozi nozzle that is kind of oval shaped the water has to go through before it hits the Pozi. Does it need to match the diameter I bore the nozzle to?

The Pozi is supposed to be 92mm. Think it will be okay to go to 94mm? Will it help me, with all the weight I carry in the boat, to get out of the hole a little better and slow the engine a little to keep at planing speed?

 

[Bondo]

Re: How to bore out a Pozi Nozzle on a Jet Drive

Ayuh,... Has this boat EVER performed properly,..??

Exactly, What have you changed since it quit performing Properly,..??

 

[mrtoybox]

Re: How to bore out a Pozi Nozzle on a Jet Drive

Hey Bubba1235, thanks for the trerrific info on how a jet drive works. My pump according to the SN tag is a 770 with a 345 Stage. I added the Pozi nozzle before I took the wet foam out and the boat worked great. When I took the wet foam out the boat ran great with the Pozi nozzle at 92mm and hauled 6 divers and gear (weigh overloaded by the way).

The performance seemed to change literally over night. The only change I physically made between great performance and poor (while loaded) was using the boat several times diving and then changing the oil.

I'm going to weigh the boat and see if the new foam has failed and is again taking on water. I'll let you know what I find.

Thanks again for the help.

 

[mrtoybox]

Re: How to bore out a Pozi Nozzle on a Jet Drive

Hey Bond-o, The boat was running great when I took the foam out and added the Pozi nozzle. It got up on plane with 6 divers and gear. I used it to dive out of several times after that and it was fine.

Then it sat for a month or so. When I took it out after changing the oil the performance was totally different. I';m gonna weigh the dang thing and see if the new foam failed somehow. Thanks again for the help and I'll let you know what I find.

 

[Lone Duck]

Re: How to bore out a Pozi Nozzle on a Jet Drive

What Bondo said. I think you would be better off spending your cash on twin motors and pumps. But it's your money my friend . Have fun.

 

[mrtoybox]

Re: How to bore out a Pozi Nozzle on a Jet Drive

Thaks again for all the suggestions. Here's an update on the boat. I bored out the nozzle to 94mm and got an increase of 150rpm and about 2-3 miles an hour more top speed. The Pozi nozzle is made so I can't go any larger because of the thickness of the wall of the nozzle.

I dug into the new foam to see if it was holding water, because Almar can't give me the weight of the boat dry. It is a 1990. They gave me the build sheets but no weight. Anyway, back to the foam, there were some areas in the foam that had voids in it where the pour left some gaps, and it shrunk away from the aluminum etc. So it had some water in it but the foam isn't holding water like a sponge. I just find it hard to believe that there could be 40-50 gallons (400 lbs) of water or so, in any or all the voids. I drilled some holes in the frame and struts to drain water out of some of the voids. I'm gonna put the floor back on and go use it this weekend and see if I got anywhere.

I'll let you know. Thanks again.

 

[mrtoyboxcouk]

Mrtoybox

Mrtoybox

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Thanks