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Old 13 July 2012, 03:18   #1
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2 or 1 engine

Hi folk... I'm looking for some advice for my 4.6m rib.
Firstly has anyone ever heard of Elite Ribs?
Secondly, I removed the evinrude 40hp 2 stroke and had a go fitting a honda 20hp. Myself, some gear etc manage 19 knots which is not bad for a 20.
With 2 in it won't plane. At about 16 knots I get 3 miles a litre. Over 2.5 at max revs.
What I would like to do is either fit a second 20 (there is room) or get rid of the 20 and fit a 50 Honda. Any one got any advice...
Cheers
Danork
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Old 13 July 2012, 03:38   #2
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OK - firstly go search the forum for something like 'twin versus singles', make sure you find some of 9d280's posts...

You need to decide if fundamentally you need/want twins (e.g. for safety) if you will actually be able to rig it with redundancy (e.g. fuel and electrics).

And if its worth any downsides... ...i'd have though 2 4stroke 20s on the transom was quite a weight...
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Old 13 July 2012, 04:26   #3
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Thanks for that. I'm away today, but when I get back I'll read the twin v single posts. Yes, 2 x 20 will weigh more than the 50.
Can't believe how much a new 50 costs!
Cheers
Dan
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Old 13 July 2012, 05:07   #4
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Was there something wrong with the evinrude 40 you removed?
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Old 13 July 2012, 06:44   #5
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Quote:
Originally Posted by Danork View Post
Any one got any advice...
Sure. Put the 40hp 2-stroke back on!
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Old 13 July 2012, 11:26   #6
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What's your 20? You might be amazed at how lardy some engines can be - My old Suz DT25 (supposedly lightweight 2- stroke) clocked in at a mere 7Kg lighter than my current 60!

Assuming it's a new honda 50 you are thinking of, they are remarkably light for a 4- stroke. As are some of the new Yammies. But as Pol says, if you are out Orkney way, there may be an argument for living with a few extra Kg so you have a "20Hp aux" rather than a 4....

There is a fair amount to consider in this twin / single arena - but whatever happens, just remember that what may be true at 300+Hp is a whole different kettle of fish at the 50-ish HP end of the scale

Post back if your searches raise more questions.
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Old 03 August 2012, 15:32   #7
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Well I've done a good bit of reading and had good advice from Clyde Outboards.
The impression I get is that 2 x 20hp will get me more safety but bad everywhere else. Fuel, weight, maintenance etc.
Since my last post I probably have covered more than 250 miles. Mostly quite remote sea areas. If my outboard packed up it would take a long time to get home with the 3.5 hp. 4 or more knot tides are everyday occurrence.
I keep on going back to the idea of the small twin idea. Would it be mad?
Do you think I would get 25knots if I get 19 now? Would non counter rotating props be a nightmare...
I like the idea of a 50 hp but the size of my RIB would preclude me ever using all the power 99.5% of the time.
I like the size of my rib and don;t think I will upgrade in size anytime soon. So I want to make this as sea safe as poss.
Thanks for your thoughts
Cheers
Danork
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Old 04 August 2012, 01:38   #8
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Have you got twin fuel tanks, twin batteries and two completely independent systems so if one fails you can run the other?
Things like been able to link the batteries will help, also consider would one engine of a twin setup up get you back home or will you need fuel cocks so both tanks feed one engine?
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Old 04 August 2012, 02:26   #9
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Originally Posted by Danork View Post
The impression I get is that 2 x 20hp will get me more safety but bad everywhere else. Fuel, weight, maintenance etc.
Think that about sums it up really. Depends then on your personal preferences/priorities. Then if you choose to go for the safety side, the more else you can practically duplicate the more safety you get. So we have twin engines and separate batteries and electrics but with a good size built in fuel tank already in there, duplicating the fuel supply is a bit trickier simply for want of somewhere convenient to put another tank. It can all be done, just a question of how much effort you choose to put in

Clearly you burn more fuel with twins, on the other hand when you're not in a hurry you can poddle around on one and probably burn less than a larger single would
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Old 04 August 2012, 03:07   #10
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Most twin engined boats I have had do not plane on one engine so you probably will not go much faster with one of 20hp motors not working than using a 3.5hp.

I know you can plane with a single 20 now, but add the weight of a second 20 and rigging on the transom and perhaps another battery in the boat and it may be a whole different story.
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