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Old 21 August 2013, 04:56   #1
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Country: UK - England
Town: Gloucester
Boat name: Lunasea
Make: Ribcraft
Length: 5m +
Engine: Suzi 140
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What engine for a 2.6m SIB?

My 2.6m Zodiac SIB currently has a Mariner 4stroke 4HP. The boat is rated for a max 6HP.
With 4 on board the 4HP seems rather under powered.


If I were to trade up to a 6HP is there a difference in weight or do 6's uses same block as a 4, and what should I go for / avoid?

I'm assuming I'll be unlikely to find a 2stroke 6HP anywhere .

Cheers,

LT
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Old 21 August 2013, 05:00   #2
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Country: UK - Wales
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Boat name: Mr Smith
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Not sure, different brands have different hp across different blocks.

Best way is to check the weight hanging off the transom really, that's probably more important too.

I have a 2hp on a 2.5 rib

What's your 4hp? Let me know if you're selling if its reliable.
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Old 21 August 2013, 06:12   #3
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Country: UK - England
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Make: Zodiac
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Engine: Tohatsu 9.8
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The 6hp Mariner is the same as the 4hp, apart from the fact it has a separate fuel tank.
It looks the same (apart from the fuel filler on the top of the 4hp) and weighs the same.

You will notice the extra 2hp of "power" after all it is 50% more than your 4hp.

I had a 6hp on my Zodiac 2.85m and it went very well, achieving 14-15mph with two of us on board. However it would not plane with three people on it.

My boat is rated to 8hp but I now have a Tohatsu 9.8 two stroke on it, which weighs the same as the Mariner 4/5/6hp engines.

This is slightly over the rated HP for the boat, but it does go very well. What it means is that I can do 15-16mph without the engine being flat out.
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Old 21 August 2013, 06:22   #4
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Make: Maxum
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With 4 on board I'm not convinced the extra 2hp will make any difference, it still wont plane and I would guess it will only give you an extra 1 or 2 mph.

IMHO I would look for a bigger boat and bigger motor if you want to go quicker with 4 on board.
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Old 21 August 2013, 16:55   #5
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Country: UK - England
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Yes four people on a little boat like that will struggle to do more than 5-6mph.

I am not sure my boat would plane with four adults on board with my 9.8hp Tohatsu.
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Old 22 August 2013, 16:14   #6
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Country: UK - England
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We use it on the river where speed limit is only 6kts, However with my RIB head on more is best.... 6HP is must be better than 4HP if the hull can take it!
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Old 22 August 2013, 16:19   #7
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Country: Denmark
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I think the lightest 6hp is the tohatsu- at least it was when I got it. Had one for a few years. Fine engine. Also has thru prop exhaust. Worth considering?
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