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Yamaha hp upgrade.....

Tue Aug 08, 2017 2:31 pm

Hi all,

Spoke with somebody today who works with outboards and he told me that its very simple to upgrade a 10hp yamaha to a 15hp by simply upgrading the reed block? All carbs are the same etc and this is all you need to do.

Can anybody confirm or quash this? I know they share power heads but id of thought their would be more to it than that......

Re: Yamaha hp upgrade.....

Tue Aug 08, 2017 5:34 pm

Not sure on the Yamaha. But my Suzuki df9.9 was a simple carb swap to get it to a 15, I think Andy B has done the conversion on something else, and I'm sure I've seen something before on swapping the reed block but cannot be sure

Re: Yamaha hp upgrade.....

Tue Aug 08, 2017 9:48 pm

Yep,
Yammy 9.9 2 strokes are simple :D
Pre 1995 OB's have a 4 petal reed block, these need to be replaces with a 15hp reed block (6 petal)
Post 1995 OB's already have a 6 petal reed block.
In this case you can either replace this with a 15hp reed block or simply open out the reed stops to 25mm gap between them.

Also check that the carb butterfly is opening fully to the horizontal position. Make sure the engine is in gear (not running! Obviously ;-) )

Re: Yamaha hp upgrade.....

Wed Aug 09, 2017 9:01 am

Happy days thanks andy. Glad it is as simple as he said.
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