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Old 22 October 2014, 03:59   #1
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Country: UK - England
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9.8 or 15 outboard dilemma

I've currently got an Avon 310, old style with ply floorboards and inflatable keel. It's rated for 10hp max and is very very rarely used with <2 people.

It's currently got a 9.9 Johnson on the back that is on it's way out and needs replacing.

My dilemma is that the boat will likely be replaced in a year or two's time, at which point I'll be looking to get a 3.8m.

I'm looking at the Tohatsu's, do I get the 9.8 which has the advantage of being very light and just accept that I'll have to get shot when I replace the boat,
OR
do I take the risk and get the 15, don't use it at full throttle but actually have something that I can use on future boats.

With the current 9.9 it won't plane with 2 people when facing the wind and when not facing the wind everyone has to move forwards (side effect of it's short size I realise), but when it is planing it's getting 18-19 knots. I'm hoping that with the 15 that planing would no longer be an issue. Or am I just experiencing old age and some of the horses have escaped from the Johnson and the new 9.8 would be a different beast? or is it simply that it's too short?

So my question to you all is, what would you do? Buy the 150 cheaper, smaller model and then replace in 2 years time, or get a 1/3 larger engine than the boat is rated for, don't use it fully (but it's still there if you get into trouble) but keep it long term.

Thanks
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Old 22 October 2014, 04:17   #2
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A 10hp should plane your Avon 2 up unless you are heavy or carry loads of other kit. We had a Tohatsu 9.8 on an older Zodiac 3.1 with plywood floors and that would plane with 2 adults or 1 adult and 2 small teens. They are the ideal motor for your Avon.

Perhaps the old Johnson is tired?

If you buy a Tohatsu 9.8 this time of year you should be able to sell it on at a profit (or lose nothing) one spring/summer when you need to upgrade.

Having said that there is sense in finding the right 15hp now to save the hassle of changing in the future. In truth assuming your Avon is still sound the extra power isn't likely to make it fall apart and as it's rated to a 10hp the weight will be fine as nearly all 15s weigh the same as 9.9s.
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Old 22 October 2014, 04:21   #3
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Thanks Fenlander,
That's very much the conclusion I'd come to.
The Tohatsu 9.8 is very light because it's an upgraded 8, whereas the 15 is a crippled 20.
The dry weight for the 9.8 is 37KG vs 52KG for the 15.
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Old 22 October 2014, 04:39   #4
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Where are you getting those weights from... are these new 4-strokes? All my comments related to used 2-strokes.
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Old 22 October 2014, 04:41   #5
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The tohatsu website, and yes, new 4 strokes
Tohatsu 9.8hp outboard
Tohatsu 15hp 4-stroke outboard
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Old 22 October 2014, 04:49   #6
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Ah, sorry, I didn't specify in my original post. I'm looking to replace with a brand new 4 stroke (only as new 2 strokes aren't available new anymore)
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Old 22 October 2014, 05:02   #7
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Oh well that 15hp Tohatsu is a terrible power to weight ratio for a small sib and really too heavy to lug about. A 20hp Honda 4-stroke weighs 6kg less.

And the 9.8 4-stroke weighs more than a 15hp used 2-stroke.

I really can't get my head round putting an expensive heavy 4-stroke on a small SIB.
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Old 22 October 2014, 05:26   #8
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You won't find much support for 4 strokes on SIB's on Ribnet - we all use 2 strokes - the 15 Mariner/Mercury is the perfect SIB engine being the lightest 15 and very user friendly. Smaller and lighter is the Tohatsu 9.8 but obviously what you gain in weight and fuel consumption you lose in oommmppphhh.
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Old 22 October 2014, 05:29   #9
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The move to the 4 stroke was purely to do with the perception of a more reliable engine (despite being more complicated) plus being backed by a warranty and further complicated by the low availability of young(ish) and/or well maintained 2 strokes.

I agree that the 2 strokes are preferable, especially as they won't empty a litre of oil into your car boot when put on their wrong side!

Looks like I'll have to keep looking for 2 strokes!

Thank you both.
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Old 22 October 2014, 05:32   #10
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I would forget a 4st and get a nice 15hp 2st not the best example but something like this Yamaha 15Hp Outboard 2004 Short Shaft | eBay 36kg nice and quiet too for a 2st
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