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Old 17 November 2009, 13:09   #11
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I don't know if I can agree with that advice.

I have that exact same RIB -- Avon 340 -- which I use as a tender for a large sailing yacht. It has a Mariner 25 horsepower 2-stroke and jocky console. It planes happily and efficiently with up to about four people and no gear, but beyond that load it starts to struggle. With five adults and some stuff it will not plane.

I would not want less than 25 horsepower, myself, on that boat. It's a real plodder when not planing.

2-stroke or 4-stroke is a matter of taste, but I like 2-strokes myself, for their unbeatable power to weight ratio, and simplicity. You give up something on economy and perhaps longevity; these will be bigger issues if you use your RIB for any kind of continuous duty. For a tender it's not a big problem. The Mariner is quite quiet; I don't know about other 2-strokes.
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Old 18 November 2009, 04:29   #12
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Id defiantly go for the 25 2 Stroke, Had a Mercury 25 2 Stroke on my old rib - Valiant 3.80

Did about 27 knots!
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Old 06 May 2013, 09:37   #13
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Hi, I realise this is an old posting, but just joined the forum and I am considering getting a new Zodiac Cadet 340 RIB with trailer. So wondering about outboard options. Suzuki 20hp was recommended but wondering about 4 stroke vs 2 stroke and possibly going for smaller 15 hp and not necessarily Suzuki. Having seen your discussion from 2009 I'm guessing you now know what worked for you. Any thoughts that might help me in my decision?
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Old 07 May 2013, 02:49   #14
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even if you go for 20hp, I would still look for a 2 stroke! I think for smaller crafts the advantages outweigh the disadvantages. My 25hp 2 stroke is fine on fuel and I was surprised I.e. pulled a knee boarder for 1 hour and a half at 3/4 throttle and I only used a few liters.

With the 2 stroke you will have more talk so will be able to take a bigger load, you will have better acceleration, better top end speed. Once you got your wind in the hair flying along at 30 knots (one person on board) you won't even notice the extra noise
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Old 08 May 2013, 04:49   #15
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Everything else aside, on a "small" boat weight distribution is crucial, and the extra Kg will be noticed. Alsio should you decide not to use the trailer the extrra weight will be noticed when lugging the engine around, and 4- strokes are more fussy as to how you lay them down in the back of the car......

Two reasons to actively go 4- stroke. If you do a lot of "pottering" / fishing the 4 will drink less at low RPM, and will be a, lot quieter. If you spend the time razzing about with a wide open throttle, chances are the difference will be negligible.
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Old 08 May 2013, 05:05   #16
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I originally fitted a Tohatsu 18hp 4-stroke, but later upgraded to a Suzuki DF25 as the 18 struggled to push the boat over the 'hump' with two or more aboard. The 25 made a big difference, and fuel usage actually dropped as it would happily hold on the plane at lower revs than had been needed with the Tohatsu.

Personally I preferred 4-stroke over 2 for the reduction in noise and exhaust fumes, though I accept that a 2-stroke may well have improved the ability to get on the plane and the weight distribution. The Avon had a power and weight limit for the transom so worth checking whether the same is true for the Zodiac Cadet as this may restrict your choice.
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Old 08 May 2013, 05:47   #17
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Thanks for the advice. It has helped to narrow down choices, so currently thinking I'll go for the new Suzuki 20hp 4-stroke at 44kg. Max allowed is 25hp, max recommended is 20hp.
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Old 08 May 2013, 14:11   #18
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Quote:
Originally Posted by Island Ribber View Post
Thanks for the advice. It has helped to narrow down choices, so currently thinking I'll go for the new Suzuki 20hp 4-stroke at 44kg. Max allowed is 25hp, max recommended is 20hp.
If you can afford a 25hp I'd go for it. It is heavier than the 20hp, but won't increase overall laden weight (boat + engine + crew) by the 20% that you'll be gaining in power, and it's costly to buy a 20 and then wish you'd gone for the 25 (which is effectively what I did).
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