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Old 20 April 2015, 10:22   #11
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Old 20 April 2015, 10:23   #12
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my 8hp yam will run flat out no probs.

i don't see how anyone can say 15hp is too much, i've seen boats with the same size aux as the main engine!

cheers
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Old 20 April 2015, 10:45   #13
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my 8hp yam will run flat out no probs.

i don't see how anyone can say 15hp is too much, i've seen boats with the same size aux as the main engine!

cheers



Let me put it this way. On my 7.8, the 8hp will give me 6 knots at WOT.
On my SIB, it'll give me about 15 knots.

That means I'm shoving water astern at an extra 9 knots that I don't need to be when it's at WOT being used as an auxiliary.
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Old 20 April 2015, 10:53   #14
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well if you strap your 225 opti on your sib it will probably be double what your rib gets!

there is nothing wrong with a big aux if-

1. have room for it
2. transom can support it
3. can be bothered lugging about the extra weight to/from the boat.

if it froths the water then twist the throttle back a smidge..simples.

9.9-15hp would be my ideal if i had room, opens up SIB options if nothing else.

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Old 20 April 2015, 14:24   #15
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well if you strap your 225 opti on your sib it will probably be double what your rib gets!
No, because he'll have it propped right for the job it normally does... You can't go any faster than the prop.
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Old 20 April 2015, 15:03   #16
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Prop the 15 accordingly then

Cheers
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Old 20 April 2015, 17:24   #17
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Prop the 15 accordingly then

Cheers
I don't think you can actually get a prop for a 15hp thats pitched that low.

You're welcome to prove me wrong though-I haven't checked on prop sizes for a 10-15hp for a couple of years and it wasn't a massive concern when I did.
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Old 20 April 2015, 17:39   #18
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wouldn't bother with it.

if i had a 15 then i'd just live with it at 3/4 throttle.

however, there are prop options available if you wish to do it.

Mercury 15hp Propellers, 2 Stroke - prop charts)

anyways, no need to keep going round in circles, there is no need for a 15hp on a 6m boat, a 5hp would work!

the point is the 15 would work if the OP wanted it to.

personally, i'd get upto a 9.9.

cheers
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Old 27 April 2015, 12:55   #19
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4hp would be fine but if it is also for a sib/smaller rib get a 9.9 2 stroke tohatsu.
The 18hp tohatsu weighs the same and is the same size but is only needed if used on a sib as well.
Also if you get a 4hp get a four stroke. My neighbour has a 4hp two stroke for his 20ft Sea Ray and it is so so noisy, sounds like it's always under a lot of stress.
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Old 27 April 2015, 13:08   #20
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4hp would be fine but if it is also for a sib/smaller rib get a 9.9 2 stroke tohatsu.
The 18hp tohatsu weighs the same and is the same size but is only needed if used on a sib as well.
Also if you get a 4hp get a four stroke. My neighbour has a 4hp two stroke for his 20ft Sea Ray and it is so so noisy, sounds like it's always under a lot of stress.
That's because it IS always under a lot of stress-as will be a fourstroke. You absolutely won't get away with a 4hp aux on a 6m rib.
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