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Old 27 July 2010, 16:48   #11
Country: UK - Channel Islands
Town: Jersey
Boat name: Archangel
Make: Ribcraft
Length: 6m +
Engine: ETec 225
MMSI: 235063789
Join Date: Sep 2008
Posts: 1,005
Originally Posted by Simon B View Post
Strewth, I thought it was 33% that Cameron has much to answer for in terms of inflation!
I think it is around 33% - that's what Ribcraft said, as did the engineers who look after my outboard.

GJ0KYZ is offline   Reply With Quote
Old 27 July 2010, 18:24   #12
Country: UK - England
Town: Poole
Length: no boat
Join Date: Jul 2001
Posts: 673
Originally Posted by Simon B View Post
The jet idea was to reduce possibility of prop strike on divers in water. Not to bothered about acceleration but economy could be a factor.
I'll need to be careful how I say this.... Instead of cutting them up you can suck them into the intake!

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Old 28 July 2010, 02:38   #13
Country: UK - England
Town: South Brent
Make: Aquaflyte, Razrfin
Length: 5m +
Join Date: Dec 2009
Posts: 25
Percentages, Schmentages!

Somewhere between 33% and 50%, depending on engine, gearbox, powertrain loss factor, etc etc.... The main cause of inefficiency is that the rev range on the jet unit usually doesn't marry at all well with the output from the engine so you need an inefficient gearbox with all those heavy whirly bits in to create the right bubble factor at the back end.
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Old 28 July 2010, 02:55   #14
biffer's Avatar
Country: UK - England
Town: swanwick/hamble
Boat name: stormchaser
Make: custom rib
Length: 8m +
Engine: inboard/diesel
Join Date: Aug 2007
Posts: 3,848
you need the biggest engine you can get into the boat, you then get into a weight problems, i'm thinking a yanmar 320hp, but unless you're going to put it under the console it's going to take half you're boat up, the cummins are good lumps but they are heavy, a lot of organisations (police, fire etc) use styer engines. they can be difficult to maintain without specialist tools
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Old 04 August 2010, 10:00   #15
martini's Avatar
Country: UK - Channel Islands
Town: jersey
Boat name: Martini II
Make: Arctic 28/FC470
Length: 8m +
Engine: twin 225Opti/50hp 2t
MMSI: 235067688
Join Date: Jun 2005
Posts: 3,018
Originally Posted by GJ0KYZ View Post
That's an interesting question; I think my next boat will have a jet drive since I'm only really interested in skinny water cruising nowadays.
Reckon I could build you a nice aluminium hulled jet drive rib, ever better for exploring puddles

Originally Posted by GJ0KYZ View Post
Ribcraft recommend a Hamilton HJ322 water jet drive, ZF Marine 280 1:1 direct mounted marine transmission, Centa GZ double element coupling drive shaft and Caterpillar 3126 7.2 litre diesel for their 10.5m boat (98K all in). I don't know what they'd suggest for a smaller rib.
Would like to think I could do it for less than 98k as well

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