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Old 03 April 2008, 12:06   #1
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Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
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Increase Hp for Yamaha 5hp

can this be done,
have a small SIB and a Yam 5 hp short shaft, i have to run it in first being new, But can it be tweaked and how to push out more Horses??
re jet and ign adjust maybe??
it would be great if the Sib was more exiting than i think its going to be!!
Cheers ALL
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Old 03 April 2008, 19:08   #2
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Town: Lima-Peru
Boat name: Nautile
Make: Sea Rider Boats
Length: 4m +
Engine: Tohatsu 18 /30 HP
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Quote:
Originally Posted by matt h View Post
can this be done,
have a small SIB and a Yam 5 hp short shaft, i have to run it in first being new, But can it be tweaked and how to push out more Horses??
re jet and ign adjust maybe??
it would be great if the Sib was more exiting than i think its going to be!!
Cheers ALL
If the next model for example a 6 HP would have the same cubic centimeters, lets say 100 CC compared to the same 5 HP by changing jets on the carb and placing the same jets as of the 6 HP , would have a nice converted 5 to 6 HP. If not mistaken the next Yam engine would be a 8 HP, perhaps with larger CC. Seems the 5 is a 4 with better jets & output.

As a comparison a Tohatsu 10 & 15 share the same CC engine, about 250 CC, to convvert simply change 10 HP jets for 15 HP jets, some models have air restrictors too, get rid of them.

Happy Boating
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Old 04 April 2008, 07:57   #3
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Country: UK - England
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Boat name: Osprey
Make: Osprey Vipermax
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The largest engine in that range is the 5HP so thats probebly not an option, Why not try adding nitrous that should give it a bit of oomph.

Alternatively you are looking at port modifications skimming the head to run at a higher compression etc. Not something I would suggest you do to a brand new engine.

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Old 04 April 2008, 11:13   #4
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Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
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Engine: Merc 60 Clamshell
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Quote:
Originally Posted by matt h View Post
i have to run it in first being new,
Errrr Warranty?

If it's new would you not have been easier & quicker just buying the bigger engine in the first place???? You could probably pick up a nice 6 or 8 secondhand for the same price as a new 5.......
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