Botswana 2072 160HP Outback

[okavango]

At last.
For all the other over 50 technologically challenged members out there, trying to download video from iPad, download the Google App "You Tube Capture"

Herewith the video's.

https://youtu.be/3wLK9tedJeM

https://youtu.be/npjAOCsKJaM

Enjoy

Mark.

 

[PSG-1]

VERY nice! Glad to see that my calculations for performance were about right for your boat's application. Do you plan to build a cowling to tame down the noise a little bit, and protect the engine from the elements?

 

[okavango]

VERY nice! Glad to see that my calculations for performance were about right for your boat's application. Do you plan to build a cowling to tame down the noise a little bit, and protect the engine from the elements?

Absolutely, this build is only halfway finished, did not have the patience to finish before confirming performance.
Once I have the reverse working, I will add the dog house and trimmings.
As nice as the engine sounds, it get real loud after a few minutes on the water.

Confirm your boat has both reverse and trim? Your reverse seems to work very well.

 

[brianb2247]

success good build cant wait to see more =D> =D> =D> =D> =D>

 

[PSG-1]

VERY nice! Glad to see that my calculations for performance were about right for your boat's application. Do you plan to build a cowling to tame down the noise a little bit, and protect the engine from the elements?

Absolutely, this build is only halfway finished, did not have the patience to finish before confirming performance.
Once I have the reverse working, I will add the dog house and trimmings.
As nice as the engine sounds, it get real load after a few minutes on the water.

Confirm your boat has both reverse and trim? Your reverse seems to work very well.

My boat only has reverse, no trim, unfortunately. With a passenger in the front, it runs OK, but if it's just me, when I go above 7500 RPM, it wants to porpoise a little bit. But I am using a +5 degree nozzle. I could probably try a 0 degree nozzle and see if that helps, or, maybe try adjusting the ride plate a little more.

The GP1200 was available with trim, but no reverse. The XL1200 was available with reverse, but no trim.
The GP1200 and XL1200 nozzles are basically the same, in fact, all you have to do to convert the XL nozzle for a GP is to drill and tap the lugs on the sides, and utilize those holes.

 

[okavango]

VERY nice! Glad to see that my calculations for performance were about right for your boat's application. Do you plan to build a cowling to tame down the noise a little bit, and protect the engine from the elements?

Absolutely, this build is only halfway finished, did not have the patience to finish before confirming performance.
Once I have the reverse working, I will add the dog house and trimmings.
As nice as the engine sounds, it get real load after a few minutes on the water.

Confirm your boat has both reverse and trim? Your reverse seems to work very well.

My boat only has reverse, no trim, unfortunately. With a passenger in the front, it runs OK, but if it's just me, when I go above 7500 RPM, it wants to porpoise a little bit. But I am using a +5 degree nozzle. I could probably try a 0 degree nozzle and see if that helps, or, maybe try adjusting the ride plate a little more.

The GP1200 was available with trim, but no reverse. The XL1200 was available with reverse, but no trim.
The GP1200 and XL1200 nozzles are basically the same, in fact, all you have to do to convert the XL nozzle for a GP is to drill and tap the lugs on the sides, and utilize those holes.

Yes that all makes sense.
I don't have enough time on the water yet to understand all the characteristics of the boat, but have been using the trim extensively to set the boat up with different loads.
If I am conservative when opening the throttle I can get on the plane without cavitation or porpoising (1 to 6 people on board), just by manipulating trim. As I mentioned earlier when you pitch the nose up there is a definite sweet spot when the hull releases and the boat picks up a few MPH.
Reverse at this stage allows me to hold the boat steady against the current and move the rear of the boat left and right, but not much more than that.
Interesting the reverse is more effective with trim set nose up than nose down.
I am going to try baffle the jet tunnel to divert the reverse thrust under the boat, but fear long term success lies in redesigning the reverse bucket to lower the thrust line.

 

[okavango]

Made up a new ride plate to try and improve reverse.
The ride plate is installed at an angle as on the Jet Ski with additional "wings" to prevent the jet stream from entering the jet tunnel.
Hopefully this will give some backward momentum, public holiday in Botswana tomorrow, so I will be on the water testing..
Hopefully I still have enough trim authority to set the boat up properly.

 

[Ranchero50]

Can you change the angle of the reverse gate through adjusting the cable? I don't have a huge amount of experience with reverse gates on I/B jets but would think the water flow needs to hit the top of the 'C' in the gate so it shoots out the bottom under the hull (that's how O/B's work). Since you write that it works better with the nozzle pointed up I think the gate may not be low enough.

 

[okavango]

Can you change the angle of the reverse gate through adjusting the cable? I don't have a huge amount of experience with reverse gates on I/B jets but would think the water flow needs to hit the top of the 'C' in the gate so it shoots out the bottom under the hull (that's how O/B's work). Since you write that it works better with the nozzle pointed up I think the gate may not be low enough.

The gate comes to rest against a stop, see the aluminum lug to the left of the bolt, so cannot get it any lower with cable adjustment, might have to redesign the gate.
The change made to the ride plate has improved matters somewhat, and reverse is now passable, but not impressive, still better with nozzle nose up.
For those having problems with porpoising, changing the angle of the ride plate caused the boat to porpoise violently, the boat manufacturer recommended I bend the small trim tabs at the base of the transom to negate this, I was astounded at how little they needed to be moved to remedy the problem.
Definitely an easy cheap solution to porpoising.
Will post pics when I get the boat out the water.
Loaded the boat with 11 people yesterday, 5 adults 6 kids 660 kg (1455 lbs) gets on plane in about 3 boat lengths tops at 40 MPH cruises at 32 MPH. Very satisfied.

 

[okavango]

Not a great picture but you can see the trim tab at the base of the transom, literally only 50 mm wide, bending this tab down 2 mm corrected the porpoising at W.O.T.

 

[okavango]

Three months without much progress, but have however built a decent trailer capable of carrying the boat off road.
Started work on the dog box and soundproofing the engine bay, reasonable happy with the results, but in reality only 60% of where I would like to get to.
Using a vibration damping mat and a sound absorbing cloth sandwiched between 2 x 2mm aluminum sheets to build the dog box. Sound levels definitely down, but the weight keeps going up.
Ran some tests into the delta this past weekend, enjoy the videos!
https://youtu.be/8xNGBZ6Hr84
https://youtu.be/XWMDUNskcNw

 

[bobberboy]

I'm going to just go ahead and say it, I've never had my boat anywhere close to an elephant! Not even on the hemisphere. Cool on all accounts.

 

[amk]

wow!

 

[Jim]

This is awesome!

:beer:

 

[Jim]

I need to send you a Decal for the boat to represent! :LOL2:

 

[okavango]

Thanks for the comments guys, pleased you enjoyed the footage.
It's good to be reminded of how special this Delta is, Botswana is very dry at the moment despite the abundance of water you see in the video. Elephant in particular have moved right into the channels and encounters like these are reasonably common.
Rainy season is due to start in a few weeks, but predictions are for below average rainfall, local rains however only contribute only a small fraction of the Delta's water, the bulk coming over 2000km from tropical rains in the Angolan highlands and reaching the southern Delta in about June.
I however nearly have a usable Jet Boat and will be able to run shallow, enjoying this privilege all year round.
Jim, I will proudly display the decal
regards
Mark

 

[DaleH]

FWIW I know ZERO about jets ... but Okavango - that project and this post is AWESOME! :mrgreen:

 

[okavango]

Managed to get the boat back on the floor this month, most of the bits I ordered from from the States have arrived and I can work towards getting it finished.
I started the noise abatement work last year and am quite satisfied that the sandwiched insulation layer will make the boat quiet and drivable in spite of the added weight.

 

[okavango]

 

[okavango]

Elephant's and Hippo's dislodge huge amounts of river grass which floats downstream in large mats,for this reason an effective stomp grate has been a non negotiable for a serviceable jet boat in this region, I ordered a linear actuator from progressive automation in Canada and am very happy with the result.
https://youtu.be/REiKSmL3vCk
The idea is to have a non latching push button on the console which will stroke the grate down, and it immediately returns when you release the button.