Jet Boat build thread..

[BRUMBERTY]

Righto, howdy all and best wishes for the new year.

After 15 months of deliberation, measuring, reading, researching, scrounging of parts, asking advice and generally procrastinating....

The time has come to start the transformation from plain jane 14 foot dinghy to nasty loud jetboat.

Hosed her out, and dragged her into the operating theatre for the beginning of surgery.

Now, please be gentle with me if I stuff things up here..its my first crack at this sort of caper,
If you know any more than me please speak up.
If you don't, just laugh along with me when I bugger something up.






The plan is..

Build up the ribs all the way to the top of the sides,

Run new stringers fore and aft every 300mm for rigidity,

Remove the rubber isolation stripping, shim and weld them rigid (all of them)

Remove old windscreen mount and rebuild as a wave breaking, solid windscreen,

Fill the 30 or so cracks and holes already in the hull,

Mount the xmember and engine mounts,

Cut shaft to length and install jet unit
(single stage Hamilton unit rated to 130 hp)

Form, weld and install cylindrical aluminium pontoons along sides and stern,

EJ22 in with a webber on its intake and a distributor up its bum.

Fuel tank, steering and wiring.

Then the 1000 things I have forgotten.

[Matt]

That sounds like a bit of fun you have planned there.... Nice load on the ute too. Side note did you end putting the L series Springs in the ute?

[INEEDABEER]

I'm interested to know what the chickens think.

[BRUMBERTY]

That sounds like a bit of fun you have planned there.... Nice load on the ute too. Side note did you end putting the L series Springs in the ute?

Yes indeed Matt, Will fitted them for me and the difference was phenomenal!

Big rocks or a load of wood....no probs, haven't dropped an inch yet.
Stiff as!

Mr Beer, how many fellas can say they have six girls living in their shed!
They love it.
Or until I hear a complaint, in english, they will have to live under the shed rules.

[Goon]

Guess you're gonna build a marinised cooling manifold? Only mention it as i can still see my old man screaming round the creek with his 186 holden inboard, on his own as there was no room left to sit once the manifold was installed...should be a kicking ride though!!!!!!

[Outback bloke]

I was all excited until I read you were doing one of those style jet boats. I think change your mind and put some thing like this in it. http://www.aardvark.co.nz/pjet/ It will be just as much fun but it will sound sooooooooo much better.

[BRUMBERTY]

Brett, with the greatest respect, you are nuts!

No- I will be aiming for 125 hp at the crank, which should equate down to around 96-98 hp at the water.


In 350 kg of boat, it should get me where I need to go.

Mr Goon-
Hold onto your betting slips gentleman...I am pumping sea water/ fresh water/ no water Via the jet unit straight through the engine.
Regulated via a pressure ruducer and a stainless steel thermostat.

Bugger the heat exchanger/coolant circuit/ complicatedexpensiveheavyandunreliablecrap way of doing it.

If it corrodes I will put another engine in it. I have 2 more.

I have a big, ever running pump and a limitless supply of cool water - I am using it.

[Goon]

RESPECT! I like the way you're thinking!

[BRUMBERTY]

I am trying to keep this boat as simple as possible.
Less to go wrong on the water or simple repairs if it does.

I am OVER niggling small issues with boats when everything needs to work all the time.

As I figure it, and please pipe up anyone who has an opinon, (Brett, SWK,)
The only steel in the cooling system is in the water pump, all the rest of the passages are alloy casting.

I have found two spots to put zinc annodes into the system and a spot to have a flush valve.

How much could it corrode really?
I may put a WD40 injection nozzle for after flushing.

[vincentvega]

are you planning to use this in fresh or salt water?

[BRUMBERTY]

Mainly fresh but there will be salt use as well.

[Outback bloke]

As you said who cares?

If it corrodes I will put another engine in it. I have 2 more.

I think the only thing I would be doing is changing any of the bolt on bits bolts to stainless.

T piece, ball valve and a hose fitting and you got a flush kit for when you get home.

[SUBYDAZZ]

I was all excited until I read you were doing one of those style jet boats. I think change your mind and put some thing like this in it. http://www.aardvark.co.nz/pjet/ It will be just as much fun but it will sound sooooooooo much better.

Yikes! :rolleyes:

[subybrumby]

Had a 327 chev ski boat once. One problem may be getting uniform heating through the engine. I know some ski boats have trouble with this and go for header tanks to alleviate the problem. Chevs handle the heat difference better hence one reason why they are used. Holden 308's and 253's tended to crack heads over this.

You can run the water through the water cooled manifold first to preheat before it goes into the engine. Might help a bit. I am just wondering how an alloy setup will handle differentiations in water temp throughout the engine??

Anyway...best of luck with the project...hows grover???

[BRUMBERTY]

Thats a good thought...the water in Tassie is not known for its high temps.
It would be odd to pre-heat the coolant.

Groover has his stitches out, his skin is almost grown all back,
He is not running full tilt yet as his leg swings a bit.....but we are stoked he is still with us and almost back to normal.

Thanks heaps for asking.

[subybrumby]

No worries..good to hear!!

[The Bigfella]

The issue with salt water is less about what type of metal it is in contact with, rather how many different types of metal. With different types of metal, eg aluminium and steel in the system - and salt water, you create a battery - and the corrosion can be very rapid. The salt water acts as the electrolyte and current flows between the different types of metal - eroding one of them. I've heard of engines being destroyed within a month.

....... and that is why marine engines use heat exchangers.

That said, my boat has a raw-water cooled Lister genset which was made somewhere between 1977 and 1991 - and its fine - because it is all one type of metal (hence no current flow issues).

[4xsama]

Matty,

Don't mean to sound like a doubting Thomas (or Andrew either) but do you think the hull might have a bit too much length?

'If it were me' I'd look at keeping the ally above the chine and get some 5mm plate, chop the back off and flatten out the bottom. Lots of r**ting around I know, not to mention a bit hit and miss, but the thing will be more responsive to the power you plan to unleash on the 'Flatty Killer'

Cheers

[BRUMBERTY]

Thanks Bigfella, that is fine advice.
With 2 or 3 zinc anodes in the alloy I should be pretty covered.
I will not be leaving her in the water for extended periods of time either.

After discussions with 3 other jet/tinny builders, I have been pretty focused on stopping her from cracking.

The planing delta I am creating is a flex mounted one and spreading the load over the area by packing it out with Polypropelyne tiles.

These are sikkaflexed onto rubber strips and secured in place.
True space shuttle technology here gentleman.

The impact point for running aground had also been shock insulated, giving 5mm of movement before the keel strikes.

Firstly some panel beating..


Then the jet intake hole...

Oops..


They don't call these death wheels for nothing..


This is a strong boat, please have a look at the cross section...



Adding the rubber stripping..

[BRUMBERTY]

Tiles and rubber..


Customising a tile..


The Jet Unit..


Not too heavy really..


A bit of creative weight adding..


My physics teacher would be so proud..



If it floats, shoot it with a cannon!
Lovely donation from the RS boys....Gracias amigos.


Almost ready to flip her over.