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!

I was reading through the replies and did not see a couple suggestions that
(I feel) could gain you *some* HP- porting/polishing and changing the prop.

When I raced the 20 mod hydro class, porting (enlarging the intake and
exhaust passages) and polishing (smoothing all the passages to a mirror
finish) added substantial power and often made enough of a difference to
leave the others 'in the dust'. Mind you, this is not a racing O/B we're
talking about here, but all motors could benefit from a little 'cleaning up
the ports'.

You can also experiment with different props to see which one gets a better
'bite' and better uses the power of the O/B to benefit your use of the boat
(loading, speed, etc).

Just a thought.

Then again, you could just buy a bigger O/B :-)

Larry

My turbine powered boat project;
http://www.turbinefun.com