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Old 21 August 2014, 18:58   #1
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9.8hp Tohatsu and 3.2m Dinghy

Hi

My Dinghy is rated for a 15hp engine. It's 3.2m

4 stoke 15hp is pretty heavy so I was wondering if a 9.8 4 stroke Tohatsu engine will have plenty of power for some decent speed?

I heard a 2 stoke 15hp is what I should be aiming for as they are lightish and quick but I'm not having much luck finding one.

Thanks

James
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Old 21 August 2014, 20:10   #2
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A 9.8 will get you easily on the plane if you're alone. 15 hp would be better but 9.8 should be enough.
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Old 22 August 2014, 02:13   #3
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I Have a 9.9 4 stroke on my 3.3m SIB which planes easily with 2 adults and 2 children. I get about 16mph (nearly 14 knots) flat out which isnt too shabby when sat that close to the wet stuff! My 9.9 weighs 50kg and is just about managable on my own.
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Old 22 August 2014, 03:23   #4
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9.8 hp 2 stroke is the perfect engine for that SIB. Modern 4 strokes are mostly much too heavy and don't have the pick up.

They are not that rare and appear on eBay every few weeks or so.
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Old 22 August 2014, 11:36   #5
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I'd much prefer a 9.8 hp 2 stroke over the 4 stoke ones. The ones I have seen go for the same price as a new engine, but you have to by them for commercial use which I can't do.

I am keeping my eyes open for a 2 Stoke engine, may as well go 15hp if it's in my price bracket
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Old 22 August 2014, 12:06   #6
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800 to 1200 should buy a decent example secondhand, or I'd go for the Mariner/Mercury 15hp - I use one of these now and sold my Tohatsu a while back.

It's the lightest 15 out there, very nicely made and the in-built gear shift on the tiller is a joy to use as is the 'lift and drop' tilt/trim mechanism.
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Old 24 August 2014, 15:29   #7
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I have a 2.85m Zodiac and initially had a 6hp Mariner four stroke.

The boat would plane with two on board, achieving about 14mph.
However it took a fair few seconds to get out of the hole.

I changed the engine for a Tohatsu 9.8 and with that on the back the SIB goes like a rocket, planing instantly two up and easily exceeding the maximum hull rating of 17mph.

The Tohatsu 9.8 weighs 26kg, the same as a 4/5/6 hp four stroke.
Contrary to some reports, ours will troll along the canal for hours at just above idle speed without complaining. The power head does shake a bit at these speeds, but as it's rubber mounted it does not transfer to the tiller.

Run at WOT (not on the canal lol...) the engine was doing 5500 rpm. I tried a higher pitch prop and it still planed easily, but took a few seconds to get going.
Maximum speed was similar, around 20mph, fractionally less with two of us on board.
However the engine RPM was about 500 lower for any given speed, so a fair bit more refined. WOT RPM was about 5,000 so maybe the standard prop is better.

I keep changing between the two.
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Old 24 August 2014, 15:33   #8
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What's the max hp on the Zodiac?
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Old 25 August 2014, 04:17   #9
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The Zodiac 2.85 (solid floor, air keel) is rated to an 8hp maximum, with a maximum transom load of 38kg
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Old 25 August 2014, 04:33   #10
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I've currently got a Mariner 15hp 2 stroke short shaft for sale as well as Honwave T38IE due to a recent rib purchase.
Engine is excellent and goes really well and is lightweight which for a SIB is one of the best power- weight available
Engine 2002 in very good condition- Selling engine for 800.
Located Christchurch Dorset if interested. PM me if you're interested
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