On Sun, 22 Aug 2004 17:39:45 -0400, "IBNFSHN" wrote:

There is a lot more to it than just carb jets. For instance a kit to upgrade
a 9.9 to a 15 runs you about $800.00. That is according to my local Johnson
dealer.

A few years ago I did extensive examination of parts microfiches to
find out the difference between my Evinrude 20, and the 25 and 30
models which are all the same block. I posted the details here.
The difference is air/fuel in and exhaust out and maintaining the
balance. I ended up opening the intake manifold restriction with a
dremel tool to equal that of the 25, and installing the main jet
specified for the 25, effectively converting the 20 to 25 hp for the
price of a jet ($7.)
Going up another step to 30 hp would have required enlarging the
exhaust output (drilling a small hole), which would have entailed re
and re the power head, new gasket kit, etc. I didn't want to go that
far.
I suppose it wouldn't be that easy with more modern engines due to the
electronic FI systems, but maybe one could simply replace a control
module in addition to mod.s as above.

Scott W.