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Old 21 September 2017, 16:36   #1
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Country: UK - England
Town: Weston-super-Mare
Boat name: Lemaura
Make: Jets Marivent
Length: 5m +
Engine: Evinrude etec 50hp
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75hp or 90hp

Does anybody know if there is a noticeable difference in pull out power between a 75hp and 90hp outboard. I have a 5m rib that is definitely under powered with a Evinrude Etec 50hp?
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Old 21 September 2017, 22:50   #2
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Country: Ireland
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I would expect that a five meter rib would have sufficient power at fifty hp especially with an etec as they have plenty of grunt. What type of rib have you and what do you do with it?
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Old 22 September 2017, 00:55   #3
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Country: Slovenia
Boat name: NM500
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I also have a 5m rib with Yamaha 50 4 stroke which is evident underpowered.
The boat have the possibility to install 100 hp max and I am thinking about 75 or 90 etec.
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Old 22 September 2017, 05:12   #4
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Country: UK - England
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75hp or 90hp

I need to be able to pull up a mono skier. The prop on the Evinrude is ridiculously big - about 21 but even so, it strugled even pulling up a wakeboarder. The rib is a Jets Marivent which I haven't heard of before but seems to be great. I have been told that sometimes a 75hp has just as much pull out grunt as a 90 so not sure. Don't know if 4 stroke may have better low end even though heavier?
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Old 22 September 2017, 06:47   #5
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Country: Ireland
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I suspect you have a problem with the pitch of the prop rather than the size of the engine. My rib 4.9m cannot achieve WOT with a 13 by 21 ali prop. I can use either a 13*17 or a 13*19 prop. I tend to use the 13/17 as it gives acceleration and watch out for over revving of the engine. However You may find you are causing the engine to lug using a 13.25 by 21 prop. This is very bad for the engine and will cause mechanical failure of an expensive kind.

Before you change engine change the prop and then check the engine height. I would probably go for a 13*17 prop from steel developments.

TSM
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Old 22 September 2017, 07:19   #6
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Country: UK - England
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Boat name: Lemaura
Make: Jets Marivent
Length: 5m +
Engine: Evinrude etec 50hp
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Believe or not, i have just found a stainlees steel 13*17 prop in my store room full of boat jumble so will see if fits.
Thanks for the advice.

Chris
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Old 22 September 2017, 14:41   #7
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Country: Ireland
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Revert with the results
Tsm
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Old 22 September 2017, 15:51   #8
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a 5 m with a 50 will be pants really, 90 -100 ideally i would say
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Old 22 September 2017, 16:50   #9
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A 5m with a 50 isn't going to set the world on fire but should pull a skier you'll only be looking for 25-27mph ish?
The 21"prop is probably your problem dropping to a 17 should help you. Engine should be able to get max rated rpm at wot with relatively light load. IE if rpm range is 5500-6000rpm aim it get 6000rpm or just over at wot fully trimmed.
Don't worry about over revving, the engine will have a rev limiter to prevent damage far better to be under propped slightly if your pulling a skier than overproped and risking engine damage
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Old 22 September 2017, 17:08   #10
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Quote:
Originally Posted by Escapeskiing View Post
Believe or not, i have just found a stainlees steel 13*17 prop in my store room full of boat jumble so will see if fits.
And the award for the best stocked store room (of expensive shiny things) goes to...
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