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Old 17 February 2004, 06:10   #1
Country: Gabon
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Power options for Gemini WR600

I am currently shopping for a new RIB to run scientific and fishery surveillance missions in Africa. Have been advised that the 6m Gemini WR600 that we are considering will do fine with twin Yamaha 50hp 4 strokes. Can anyone comment on the suitability of this combination? We require a lick of speed, but the need to spend as much time on the water as possible makes fuel economy an important issue. Any advice much appreciated.
Have looked at a 7.3m boat, but the power requirements start at twin 75s and are apparently optimum at twin 115s. this would incur a considerably greater cost at purchase, and presumably, much higher fuel consumption. Again, advice much appreciated.

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Old 17 February 2004, 07:04   #2
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Hi Parks

Are you really sure you want to go for twin engines?

I think you would be better off with a single 90hp four stroke. You would get better performance and fuel economy.

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Old 17 February 2004, 08:18   #3
Country: UK - England
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Dont know the Gemini WR600 but if you want some speed 2 x 50HP sounds a bit underpowered to me.

Twins are not as efficient as a single and I would have made a guess that a 6M rib should run upto about 150HP.

You need to decide between fuel consumption/speed of a single or the redundency/safety of a twin setup if you have a limited budget (who does'nt). You cant have both.

As far as 4/2 strokes, in the engine size bracket 50-75HP I dont think their are that many HPDI/Optimax engines. Going for a single 100HP-150HP gives you much more choice in the hitech 2 stroke market, and the good fuel consumption that goes with them.
One thing to watch for though is although 4 strokes give you good fuel consuption they are often heavier and twin 4 strokes maybe very stern heavy.

Maybe others who run outboards can help as im a diesel convert
, but I dont think I will be far out with the above.

Regards Gary
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Old 17 February 2004, 09:26   #4
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Originally posted by Phil Chitty
Are you really sure you want to go for twin engines?
Bearing in mind the operating area, I'd go for twin 60/70hp two strokes with separate fuel systems for each engine.

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Old 17 February 2004, 10:15   #5
Country: UK - Wales
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Boat name: DynaMoHumm/ SRV/deja
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Agree with DM Fuel is cheep in Africa and there is a lot of crocodiles so go for a redundant solution
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Old 17 February 2004, 10:32   #6
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Have to aggree with DM,
The twin 2 stroke route is the road I would take, with the seperate systems. Having worked off remote african coasts twins give a nice peace of mind

What is the service agents like in Gabon? I would definatly look at who had the best incountry spares support.
If you can afford it Yam or Murc/Mariner would be my choice.
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Old 17 February 2004, 14:36   #7
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Unless there are good service agents and spares support I would go for standard carburettor engines rather than Merc Optimax or Yamaha HPDI engines - there isn't anything wrong with either of them but they can be a bitch to fix if anything happens to them - plus the Optimax likes special oil!

If it's the carb engines I'd pick Yamaha's every time - the 90 HP would be my choice and 2 of them!
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Old 17 February 2004, 14:56   #8
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Engine Types

Hi Parks,

Considering the area and type of work you are undertaking, I would seriously consider a diesel engined craft ( if it burns you can run on it).

For a boat of this size I suggest a Merc diesel as ideal, as long as you do not need to faster than 35 - 40 knots.

Bearing in mind time on the water and ease of service, quality of fuel and parts availabiltiy. I would not consider a modern 2 stroke or 4 stroke for that matter, unless you can guarantee a good marine engineer with knowledge of computers and access to parts.


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