Re: 9.9 Upgrade to 15hp
'Bout the only thing you need on this year engine is a carb change out. Would you see a difference? Questionable unless you know the rpms before and after the change over.
WOT rpms between a 9.9 and 15 is (if I remember the service manual right) 500rpms....could be more.
If your trying to get better performance out of the 9.9, try working with the engine set up on the boat and the prop before modifying the engine. Set up works wonders. Try and get the anti-cav plate at least 1" above the keel of the boat. Change the prop out to a 9.25 X 8 prop (9.9's and 15's come with the standard 9.5 X 10 prop). Once on the water, adjust the tilt bar for best performance with a normal load. You might be surprised at the change in performance.
