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how much power ?

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1 how much power ? on Fri 23 Apr 2010, 4:12 pm

Little Lucifer


Vice Admiral
Vice Admiral
got my haynes hellyer today i recon it about 15% step up so how much power am i going to need ? i want to put it in a 18ft front seater glass hydro its got a dog clutch should i keep the dog also do i want the prop spining left or right hand ?

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2 Re: how much power ? on Fri 23 Apr 2010, 4:21 pm

doug (tiller steer)


Sub Lieutenant
Sub Lieutenant
about 2700hp, 40 in pitch clever. allison jet turbine engine.

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3 Re: how much power ? on Fri 23 Apr 2010, 4:42 pm

Little Lucifer


Vice Admiral
Vice Admiral
if i can find one in the scrap i will get it but at this stage i have a pick from a twin cam toyota 7me 3 lt a couple of 5 lt holdens 2x 327 or a 350sbc and a big banger 454 bbc

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4 Re: how much power ? on Fri 23 Apr 2010, 5:08 pm

doug (tiller steer)


Sub Lieutenant
Sub Lieutenant
go the toymotor. with a huge huffer hanging from it........

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5 Re: how much power ? on Sat 24 Apr 2010, 1:16 am

The Spook

avatar
Admiral
Admiral
Simon

Go for the minimum amount of motor to start with. This allows for you to learn to drive the boat without scary things happening which you are not expecting. Then after a couple of seasons step up in power a bit and get used to that. Then if you still want to go faster then think about what the hull is capable of and how much it will take to put that edge on its performance.

When I bought my old hull it came with a 253 holden in it and it never felt like it was enough engine for the hull but it allowed me to learn how to drive the hull and what it could do. After about 2 and a half years I built my first 308 for it. The first 308 was pretty mild but it transformed the hulls performance,not because it was a hot engine but because it was enough engine for the hull and prop/gearbok ratio. it had a top speed of about 175-180 kph.

The second 308 was the one that put the edge on the boat. It would spin 8000 plus rpm and pushed the accelaration and top speed right up there. My mates and I believe that it was up around 200 kph. At that stage the boat had a fair edge to it and it was a real buzz to drive.


The point of this drivel is really to point out that by working up to the hulls performance capabilities it doesnt scare you when you actually get it up there, mine was a handfull to drive but it wasnt scary

The prop that you will be looking for will be a three blade cleaver style with a clockwise rotation when looking at it from the rear. Menkins in the US do one. What you will need will have a diameter of about 10.5 to 10.75 inches and about 17 to eighteen inches of pitch. If you run a modest 5 ltr a gear ratio about 10 to 12 percent step up will be a ballpark starting point.

Just a piece of advice about building an engine for hydro, dont go for a big camshaft, something middle of the road is best. Best to start out with a very modest engine and work your way up.

Also remember that a hydro does everything differently to any boat you've driven before, so take it easy.

Bob

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6 Re: how much power ? on Sun 25 Apr 2010, 10:13 am

your gear box is going to suck up over 10%horse power so chuck it in the corner of your shed.run of the snout of your crank..that will give you the right rotation. if you run that way you will need to pin your balancer also that adds strength to your keyway..theres props around that you can use for that set up.im getting a collection of them at the moment..i have 3 .depending on your engine you can get them cut down and changed to suit your combination.remember to angle your turn fin in 10 to 15 degrees from verticle.your rudder needs to trail .dont set it up verticle or you wont be able to steer the boat..it will be like a twitchy bitch and dart allover the track..cheers gary..

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