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Old 05 September 2016, 13:48   #1
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Country: UK - England
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Extra 5 horses

On my little 3.4 m Valiant rib I have a 15 hp Mariner 4 stroke. It performs quite well and I can get about 20 knots out of her with just me on board. I found out today that my engine is in effect a detuned 20 hp and I spoke to the UK importer and he said I can replace the Carb and it will hey presto be a 20 hp engine. I have not yet found out the price of the carb but I suspect it will be on the order of 250 plus.

Do you think that an extra 5 hp will make much difference to the boats performance

Dennis
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Old 05 September 2016, 15:32   #2
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With my 25 I get with everything in its favour 24 kn mostly 22 kn 1 up and kit Mercury 365 you might get a kn or two but you will get better fuel consumption knocking the revs back a bit.
Since you got pin position right you could try lifting the engine an inch see what happens just a block of wood if it don't nothing lost
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Old 07 September 2016, 16:37   #3
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That's a big % increase! But would you need to change the pitch on the prop to get the best out of the upgrade?
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Old 07 September 2016, 17:54   #4
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Originally Posted by HDAV View Post
That's a big % increase! But would you need to change the pitch on the prop to get the best out of the upgrade?
I'd expect to see an increase (perhaps 25 kts max?) but you'd expect to have to change the prop to get it.

Is it really just a carb? no timing to change too?
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Old 08 September 2016, 01:23   #5
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I'd expect to see an increase (perhaps 25 kts max?) but you'd expect to have to change the prop to get it.

Is it really just a carb? no timing to change too?
The UK division of Barrus who is the owner of mariner and mercury told me it is just the carb and if you look at the brocure it does look so

Dennis
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Old 08 September 2016, 02:34   #6
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For swapping OBs on my 3.8m SIB from a 15hp to 20hp I've gained about 2kts on max speed but I'd expect a slippery GRP hull to make a little more of any power upgrade.

Mid range grunt is the biggest improvement and where it's actually more useful in difficult conditions.
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