Don't know about the 15 hp, but I do know that incresing fuel/air flow
increases hp for car engines.
I like the idea from Robb suggesting trying a carb off a larger motor.
Changing the mix won't increase hp. Variable Ratio Oil (VRO) pumps adjust
the mix from 50:1 to 100:1 based on manufacturer speced lubrication
requirements for the operating range RPMs.
Going to a 100:1 will burn cleaner, but not properly lubricate the engine
thru the RPM range.
MMC

wrote in message
oups.com...
O.K.: Urban myth or not?

I've heard over and over again that everything is the same on a 7.5
h.p. Johnson as on the 15 horse, except the carb. I also heard it's
not even the carb, it's just the jets.

I have a 1980-ish 7.5 seahorse that just does not have the guts to pop
my inflatable up on plane with two people and a full tank aboard. I
added those wings, which do help, but still just need a little more.

Anybody actually done this carb or jets upgade, or at least seen it
work? Every dock rat seems to have heard of it, but nobody's done it.

Failing that, any ideas on how to squeeze a bit more out of a
two-stroke (short of going 100:1 on the mix)?

Thanks!