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Old 23 May 2013, 02:40   #1
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twin outboards?

As previous posts, next project is a 6mtr ish rib with twin 90s on the back.... Question is do you have to have one normal 90 and one counter rotating 90 to give a better drive as would there be to much "screw" effect from 2 normal 90s or is the answer just to fit non feedback steering to offset the screw effect so you dont feel any "pull" on the steering.... Whats the general opinion,thanks
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Old 23 May 2013, 02:54   #2
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Just fit left hand and right hand props, which will give you the best result
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Old 23 May 2013, 03:24   #3
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As previous posts, next project is a 6mtr ish rib with twin 90s on the back.... Question is do you have to have one normal 90 and one counter rotating 90 to give a better drive as would there be to much "screw" effect from 2 normal 90s or is the answer just to fit non feedback steering to offset the screw effect so you dont feel any "pull" on the steering.... Whats the general opinion,thanks
You might struggle to find a counter rotating 90hp outboard, they don't usually start until 115hp
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Old 23 May 2013, 03:26   #4
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We installed twin Mercury 90 ELPTO (2 stroke) on our Parker 650. The 4 stroke engines were just too heavy. The 90 HP engines do not have counter rotation so just install standard engines. the performance is very good.

We first installed Mercury twin 60 HP 4 stroke , the weight was OK but poor performance
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Old 23 May 2013, 03:36   #5
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Just fit left hand and right hand props, which will give you the best result
Errr that might be fun if one of them doesn't have a counter rotating gearbox.....


As Andre says, ref. the size but if you really feel you need symmetry have a dig around the microfiches. Some manufacturers carried gearboxes across that sort of HP range, so you may find you can take a couter rotating gearbox off a 115-ish & park it on the bottom of the leg of a 90.....

Will need some research tho'.
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Old 23 May 2013, 03:39   #6
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If I am not mistaken the counter rotation begins from 135 HP upwards
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Old 23 May 2013, 03:42   #7
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If I am not mistaken the counter rotation begins from 135 HP upwards
Etecs start at 115
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Old 23 May 2013, 04:25   #8
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Errr that might be fun if one of them doesn't have a counter rotating gearbox.....
Very manoeuvrable, will turn on a sixpence
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Old 23 May 2013, 05:15   #9
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very manoeuvrable, will rotate madly on a sixpence
ftfy
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Old 23 May 2013, 05:22   #10
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With hydraulic steering and a bit of transom offset it would be fine. There's twin 200s around with both std rotation without problems.

Advantage is you don't have to worry about problems with the inherently weaker counter rotating gearbox.

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