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Old 24 June 2017, 01:12   #1
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8 hp and planing 3.2 m sib

I have a 3.2 m SIB with ali floor and inflatable keel. I am looking at a 8 hp Mercury 2 stroke. I wonder if this size of engine will easily plane the boat with 2 people on board

Thanks

Dennis
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Old 24 June 2017, 02:31   #2
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Worth a read through this thread Dennis... SIB not planing

Long and short of it is that with an 8hp you need all the conditions to be right to plane... minimal load... fully inflated SIB... right sea conditions etc.

There are loads of YouTube videos of folks skimming along with 8hp motors but I suspect these are often with all the ideal criteria... my experience is anything less than a 10hp can annoy by struggling to plane when any of the factors are against you.

If you are two light adults or light adult plus child I think you might be OK... as each person is heavier or you take out a large dog or loads of fuel/kit as well then it gets more and more problematical.
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Old 24 June 2017, 02:34   #3
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My 2.9m sib won't plane with 2 people aboard and an 8hp 2stroke yam, so I very much doubt you'll get a 3.2m to plane. Goes OK with one though.
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Old 25 June 2017, 02:04   #4
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If you look at this vid it seems to be fine with a 8 hp


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Old 25 June 2017, 03:05   #5
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Originally Posted by Fenlander View Post
Worth a read through this thread Dennis... SIB not planing

Long and short of it is that with an 8hp you need all the conditions to be right to plane... minimal load... fully inflated SIB... right sea conditions etc.

There are loads of YouTube videos of folks skimming along with 8hp motors but I suspect these are often with all the ideal criteria... my experience is anything less than a 10hp can annoy by struggling to plane when any of the factors are against you.

If you are two light adults or light adult plus child I think you might be OK... as each person is heavier or you take out a large dog or loads of fuel/kit as well then it gets more and more problematical.
I did read that thread and it was interesting but no conclusion yet. It looked in the end as though it might have been the engine not up to revs
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Old 25 June 2017, 03:33   #6
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>>>but no conclusion yet.

Exactly. Simple fact is you can't say if an 8hp will plane two adults in a SIB unless you try the OB on your SIB with your load in the sea conditions you experience. It works for some... doesn't for others. My experience has been more on the doesn't side.
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Old 25 June 2017, 03:37   #7
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>>>but no conclusion yet.

Exactly. Simple fact is you can't say if an 8hp will plane two adults in a SIB unless you try the OB on your SIB with your load in the sea conditions you experience. It works for some... doesn't for others. My experience has been more on the doesn't side.
I know the issue is I have the chance of a 8 hp Yam 2 stroke that is nice and light and at a reasonable price which wont of course hang around for ever. Trying to get a 2 stroke 9.8 or 10 hp near me is very difficult

Dennis
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Old 25 June 2017, 03:57   #8
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Those Yamaha 8hp 2 strokes are great motors and if you were to be solo I'd say go for it.

Could you buy from someone like Seamark Nunn who might allow you a 24hr trial??
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Old 25 June 2017, 04:06   #9
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Isn't there anyone local who will loan you one for a trial?
I've got one but we're up in Scotland.
The 8hp yam has a great weight advantage over the 9.9 & it's a gutsy little engine so if it will do your job I'd take it over the significantly heavier 9.9
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Old 25 June 2017, 05:20   #10
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Those Yamaha 8hp 2 strokes are great motors and if you were to be solo I'd say go for it.

Could you buy from someone like Seamark Nunn who might allow you a 24hr trial??
I am very close to seamark nunn and they don't have anything suitable
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