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Old 11 February 2008, 08:49   #1
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O/B Weight Differance

Hi
Can anyone tell me how much the weight of an outboard would have on performance on a 5.5m rib .For instance an E-tec 75 weighing in at 145kg verses an Optimax 90 or Honda 90 at 172kg . Would the extra 15 hp be lost due to the extra 27kg weight ?

Would a Destroyer/Oceanpro be under powered with an E-tec 75 ?.
Thanks
Tim
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Old 11 February 2008, 09:46   #2
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Hi
Would a Destroyer/Oceanpro be under powered with an E-tec 75 ?.
Thanks
Tim
I wouldnt have thought not, with the right pitch prop it would be a good motor for this size. Our club Delta had a Mariner 75 on and it went well, all be it a bit sluggish with 6 divers but then thats getting close to its designed payload.

Before power is considered do have a look at the transom rating it should be in both engine weight and max hp. Not a good idea to go over this but people do.
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Old 13 February 2008, 04:51   #3
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To put the weight difference into perspective, its about 36 litres or so of fuel.......

The difference is with fuel you can (if it's in a nice 30L plastic tank) put the weight in a sensible place to trim / balance the boat. But on a RIB that weighs in the vicinity of half a ton, probably make next to no difference
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Old 13 February 2008, 05:33   #4
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Why not an Etec 90?
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Old 13 February 2008, 09:03   #5
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Why not an Etec 90?
Its a second hand rib . Looking for something around the 5.5m with around the 100 hp etec,opti or 4 stroke and wondering if a 75 etec would be much down on performance . Usually go out with two mates both with 5.5m one with a 100hp 4st the other with a 85hp 2st and just want to make sure that I will be able to keep up to them
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Old 13 February 2008, 18:32   #6
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the etec 90 is the same as the 75 .

I tested a demmo of my 5.5 m boat with a 75 etec and it went OK with 2 aboard but i felt it could have been a bit sluggish when loaded .

the 90 had a good bit more punch and is the lightest in its class. I made my decision as much on the wieght as anything else as i feel it makes a fair difference when you can save 30 ish kilo hangin on the transom . The dealer also agreed he had tried the same boat with heavier motors and said it didn't feel as balanced or perform as well .
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