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Old 12 September 2018, 08:28   #1
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Country: UK - England
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10HP 4 stroke in Plymouth

Just a thought - trying to decide on a new engine - a 10Hp would be lighter than a 15HP but would it make much of a difference compared to my old 8hp 2 stroke.

2 up I get 12kts, reports indicated I might get 17kt with a 10HP which would be fine.

Just wondering if anyone in Plymouth area has a 10HP on a SIB?
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Old 12 September 2018, 09:16   #2
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If you are getting 12 kts with a relatively lightweight and punchy 8hp then I cannot see such a large increase in knots with just a 2hp increase.
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Old 12 September 2018, 10:27   #3
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Indeed - my 2 stroke is over 20 years old, so I dont know how much "power" it has lost - and a new engine should be reliable! I am tempted by Gazzago's 15hp but bothered it will be too heavy @ 52Kg. So Im drawn to a new 4 stroke 10hp @ 35kg..
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Old 12 September 2018, 13:51   #4
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Plymjack perhaps you were hoping this thread might throw up someone near you with a 10hp who would have an outing with OB swap. If I were in the area it would be no problem.

However I'd think I might have said this before but you could fairly accurately transpose the results across from our trials with an 8hp and 10hp on the Aerotec.

With a 2-up load 10.5kts with the 8hp became 13.5/14kts with the 10hp.

So if you went up 3kts or so you'd be at 15kts or so. Your SIB is much heavier, longer and wider than ours though so the speed comparison may be different either up or down.

Personally I don't think I'd spend a lot of cash changing for just 2hp increase. Going up to a 15hp min should be your aim.
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Old 12 September 2018, 17:03   #5
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Well a practical test would help so thank you for your comments.

Indeed that is the problem, the 15hp is also some 10-15kg heavier then the 10hp so while more desirable it just may not be practical.
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Old 12 September 2018, 18:44   #6
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Not sure if this option has been discussed for you in a different thread but how about one of the last of the 15hp 2-strokes which weighs the same as a 10hp 4-stroke?
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Old 13 September 2018, 02:58   #7
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Yep, forget a 10hp 4 stroke go 15hp Merc/Mariner 2 smoke or if it must be 4 stroke then the latest Suzuki 20hp.
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Old 13 September 2018, 05:21   #8
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Country: UK - England
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@Max & @Fenlander thank you: The latest Tohatsu 20hp mfs (same as the 15!) is only 43kg so looks like that maybe the way to go....
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Old 13 September 2018, 05:25   #9
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If you have budget for that and are happy with the weight then any of the Tohatsu/Mercury/Suzuki latest efi 20hp models around 43/44kg would be the most suitable for your size SIB and guarantee good performance rather than spending say £1700 on a 2hp upgrade to a 10hp.
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Old 13 September 2018, 11:18   #10
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Country: UK - England
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@Fenlander - thanks again..... yes found the Tohatsu 20hp and more money then I wanted to spend but Mrs. likes the idea of it being 43Kg and Economical too.... so just need to sell mine and get sorted.... will post a video once its on board.......

thanks to all for your inputs.
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