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Old 20 November 2014, 12:32   #1
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Country: Ireland
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8 to 15hp

Hi all.
Have an 8hp 2 stroke (mariner 1980s) on my Achilles 12ft sib a bit feeble and just about planes 1 man 80kg at 15mph, with two people it ploughs at 7MPH .
Question is would upgrading to a 15hp Johnson 2 stroke 2003 do the trick for say 2 or 3 people.
Thanks
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Old 20 November 2014, 12:40   #2
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What's it rated for? I usually work on slapping the most horses on provided you can lift it ?
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Old 20 November 2014, 12:48   #3
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Achilles boat is rated 20 hp. But this 15 is a very nice engine, would 5hp less make it very underpowered
Should i hang out for a 20hp
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Old 20 November 2014, 12:49   #4
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It should go very nicely with a 15hp with 2 or 3 on board. If you load it to the gunwhales though it will struggle.
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Old 20 November 2014, 12:51   #5
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hhmmm
I do like reasonable performance especially a couple miles off coast St Georges channel can run 8 knots
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Old 20 November 2014, 12:59   #6
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I can only give you my own experience with my Honwave 3.5 AE . I have a 2005 Mercury 15hp 2 stroke & a new Tohatsu 20 hp 4 stroke.
The Tohatsu gets it onto the plane quickly with five of us on and stays there at 50% throttle but the 15 we have just gets us out and has to work hard. The mercury has a stainless prop, Tohatsu standard ( no idea of pitch).
The Tohatsu is HEAVY compared to the Mercury but does use a lot less fuel.

Horses for courses really. We tend to be away for two weeks so putting the Tohatsu on/off isn't an issue but the Mercury's a lot handier for a day out especially if you have to transport it.
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Old 20 November 2014, 14:06   #7
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A 15hp 2s will do the job 2/3 people and weigh in around 36-40kg.
Were as 20hp 2s will also do the job but you are looking at 48-53kg as the 20 is usually a detuned 25hp.

I run a merc 15 and don't have any trouble moving it around 37kg, but also use a 30 Johnson which is the same block from the 20 to the 35 and weighs in at 53kg ish. So pick and choose which engine to use depending on were I launch from.

Both push our 3.8 along well just the 30 gets there quicker with a bigger smile.
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Old 20 November 2014, 14:34   #8
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OK guys Im getting the picture now , so some 20s are as heavy as some 30s ,sounds daft but I understand reasons how so.
Starting to lean towards the 15hp as dont like lugging weight about and its an old transom .
Reason i wish to upgrade engine is last September we got caught 3 miles out very strong headwinds got up took ages to get in and ran on petrol fumes for last few minutes.
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Old 20 November 2014, 17:53   #9
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i run a 15hp yamaha 2stroke on a avon 400s a fairly heavy sib it gets the avon on the plane no probs .
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Old 20 November 2014, 23:46   #10
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I run a 15hp 4stroke Suzuki on a 3.8 tohatsu
last weekend on Ullswater we had 21knts with 2 15stone men up and 26knts with one


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