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