With current 4 strokes and a 6.6 you should get at least a nautical mile to a litre.  My 6.8 hardtop is within the prados towing capacity.  You would be surprised how little fuel you use around the islands once you get there.

planning on taking mine out to the Monties from Dampier and whilst I will be taking spare fuel for safety I have no concerns 

have you put your rig over a weigh bridge with gear and fuel? What did it come out at? How much fuel do you carry? 

Fuel is always one of those things that you are better looking at it than looking for it. 400 litres is not a bad amount to have if you are using the boat a fair bit. Fine line between being practical and having plenty of juice under the floor for extended Abrolhos and montes runs and having to dump fuel because it’s going stale because you aren’t fishing enough. 

I seldom load the boat with much gear, cannot believe how much crap some people load up their boats with particularly when heading north ......tank is 200 litres....motor a 225 yammy.. when heading out to the islands we load another 200 in a bladder or drums, actually like drums as you can easily unload them and float them ashore.  

Agree on fuel. Horrible feeling running low and continually doing calculations in your head on how far you will get.

Split tanks is a good idea.  

Mate I’ve got a 5.5 genesis 

they are built tough. I’ve gone through a motor, onto the second one

  easily has 2500 hours on my hull and she’s still slaying fish 

mine has plenty of wear and tear but it’s been thoroughly flogged 

has been out in some horrible conditions and always brought us home safe 

can’t speak for redlines but they certainly look solid aswel 

good luck you won’t be disappointed either way 

put the biggest motor you can on the back would be my advice 

boat builders love keeping costs down with under powering boats at times  

Any one on here own or been on an assasin or redline 6.6? 

 I have a 6.1 Genesis

and like black Gen it's taken a beating over the 14 years I've owned it.  certainly a few thousand hours out there.  Slaps a bit in chop (sure the 6.6 would be soooo much better) but so stable to fish in.  had a few pin holes fixed over the years.  but nothing major.  Also like Black Gen have been out some bad weather but always feel pretty safe ....even surfing a big folllowing, all good.  you wont be unhappy with a Genesis.  Unsure of the redline but you defenetly wont be unhappy with a Assassin either.

I recently got a 6.1 Genesis and it has heaps of room on board. Still running in the initial 20hrs on the motor but in the line of stats, here's a few;
610xl with a Yammy 200 (4cyl) with 4 people & tackle on board in good conditions at approx 45km/hr gets an average of 2 klms per litre of fuel.
I have an inbuilt 300ltr tank which gives a return trip total of (To play it really safe) 500klms.
I had to knock it back to 35-40k/hr when the seas got big chop and was still averaging 1.6 - 1.7km/ltr.
Fuelled on trailer weighs 1700kg, which is good because over 2t normally means you need electronic brakes on the trailer doesn't it? So my Hilux drags it fairly easy.
My Genises is new but looks almost identical to the one above and I highly rate it. Hope this helps.

 .

Appreciate the feedback. Sounds like a solid rig. Good point on the brakes. I am pretty sure I will top 2t, so have to accept that I will need electronic braking.

 6.3m. was quiet blunt but great on the drift  ,think they have refined now / deeper v , red line would be great but more expensive.... 200 litre tank  plus 4 jerry cans imo would be max .. hard top would be an over kill