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Old 14 March 2006, 18:25   #1
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Country: UK - England
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Have you upgraded your hp on your engine, if so post here and tell others

If you have upgraded the hp output by performing simple changes on your engine then share this with others as it will help them out.

Many people were keen to understand how for example a 9.9 yam can be upgraded to full 15hp output in simple steps, i shared this with folks on a separate thread.

but

lots of folks are keen to understand what upgrades have been done to other engines, share what you have done and what it cost.......

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Old 14 March 2006, 18:26   #2
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upgrading a modern 9.9 yam 2 stroke to 15hp

I have had a couple of questions regarding what it takes to upgrade a 9.9 yam to a 15

here goes

i have attached a pic of my particular engine, you will note the engine plate on the side of the engine as Steve cant find his so this is where it is on my engine. this modification was done on this style of engine rather than the older squarer ones

the next pic is me pointing to a metal stop that restricts the throttle from opening more than around 60%

if the background you can see the gold colour of the reed block, this is just bolted in place between the block and the carb

took me around 20 mins to do the work and that included a t-break

another pic of the engine from the side.

costs were as follows

bending the throttle stop out the way ....free

buying a new 15hp reed block....around 28 quid

buying a new 15hp sticker for the front and back.....around 2.80 each

i purchased a 12 pitch prop to take advantage of the extra power....50 quid

the benefit of the 50% increase in performance and increased economy....priceless

it is amazing how much more these reeds open compared to the 9.9 item

well worth doing
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Old 15 March 2006, 04:49   #3
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Country: UK - England
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Send a message via MSN to stedj
cheers hugh
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Old 15 March 2006, 16:54   #4
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You can Change the HP on a 75hp Mariner/ Mercury to 90hp. Get some 90hp carbs put them on and change the max ignition timing to 18 degress and bobs your uncle!.
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Old 15 March 2006, 17:24   #5
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Quote:
Originally Posted by Turbodiesel
You can Change the HP on a 75hp Mariner/ Mercury to 90hp. Get some 90hp carbs put them on and change the max ignition timing to 18 degress and bobs your uncle!.

cheers turbo

il' look into that

andy
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Old 15 March 2006, 17:50   #6
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Quote:
Originally Posted by Turbodiesel
You can Change the HP on a 75hp Mariner/ Mercury to 90hp. Get some 90hp carbs put them on and change the max ignition timing to 18 degress and bobs your uncle!.
Or you could just stick new labels on and see if anyone notices oops boy racer coming out in me
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Old 18 March 2006, 13:33   #7
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Any Ideas To Make The 225 4str To 250 ??

need the extra power of the 250 4str of johnsons.... the pair of 225 goes up to 45knots with 16x23. a friend who has the 250's suzuki which are the same reaches easily 52-53knots with total of 4.5tonnes...mine on other hand is 3.5tonnes.
thinking of bying the "brains" of the 250's...better ideas?
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Old 19 March 2006, 15:42   #8
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Engine height can be important, do you and he get the same revs at that speed readout? Also the gearboxes might have different ratios between the Suzi and Johnstons. I havent checked, but that could account for it. I had a single installation that 'came alive' after I raised the engine 2 inches. My cav plate was above the bottom of the hull, and the result, surprisingly, was all good. Duals might be different though - just a thought
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Old 20 March 2006, 14:24   #9
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thank y bigmuz...propaly you are right about height...but propable it's raised too much....i will low 1 hole down and retest.on the other hand the suzuki and johnson are exactly the same in everything...only the stickers of different companies change!
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Old 21 March 2006, 09:57   #10
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Tohatsu

Anyone worked on a 40-50hp Tohatsu. Heard and read that the block is the same. Some 50hp carbs on the 40hp plus shaving a mil off the head creates a lot more power? Anyone done this or know of someone who has. Where are those ZapCat fanatics?
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