English: upgrading 9.9 to 15 hp

[EMA]

Just bought a 9.9 yamaha outboard 2 stroke 2004 model and want to upgrade it to 15 hp. I have heard its easy, but have no clue as to what I need to to do, can somebody help me? Thanks

[rago63]

This is quite simple; You have to remove a litte metal sheet located at the speed control mechanism where the trottle wire and magneto control wire are assembled.

 

This metal sheet is formed like a plain washer with a little 90 degree bend, and is set on the axle on this device. The sheet will prevent your engine to achieve WOT, thus stopping the control mechanism to rotate the full way. You only have to bend it avay, you don´t need to remove it completly.

 

This will extend the output to approximently 13,5 hp.

 

To make this engine increase the output to 15 hp, the reed valve stopper height need to be adjusted. The stopper height is in 9,9-13,5 versions 1,3mm. In the 15 hp the height is set to 6,0mm, both within a limit of +/- 0,1mm.

 

The workshop manual strictly recommend replacement of the stopper if it´s out of specified limit. In this case, I would say that you will have to get a new set of stoppers from the dealer - and not bend any wider the stoppers that you already have in the engine. Collecteral damage will happen to the engine if they break and goes into the crankcase.

 

Another way to come around this is to buy a set of Boyesen carbon reeds. The assembly instruction of these predicts removal of the stoppers completly. If they should break, it will normally cause no harm to the crankcase as they are made of carbonfibre - not steel....

Redigert 28.Mars.2008 av rago63 (see edit history)