can I increase outboard hp?
 

can I increase outboard hp?
 

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

can I increase outboard hp?
 

a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.

can I increase outboard hp?
 

How did you measure the horsepower?

Roger

http://home.insightbb.com/~derbyrm

"Drew Dalgleish" wrote in message
...
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.

can I increase outboard hp?
 

Drew Dalgleish wrote:
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.


For 2 and 4 stroke going back 2 decades, the 5 hp Merc is 1 cylinder,
the 8 hp is 2 cylinders.

can I increase outboard hp?
 

I took the mechanics word for it. It wasn't my motor and I didn't see
it in action . He did explain how and why he was doing it.

How did you measure the horsepower?

Roger

http://home.insightbb.com/~derbyrm

"Drew Dalgleish" wrote in message
...
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.

can I increase outboard hp?
 

And how long is your leg now.........


"Drew Dalgleish" wrote in message
...
I took the mechanics word for it. It wasn't my motor and I didn't see
it in action . He did explain how and why he was doing it.

How did you measure the horsepower?

Roger

http://home.insightbb.com/~derbyrm

"Drew Dalgleish" wrote in message
...
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.

can I increase outboard hp?
 

whatever you want to believe I guess. Perhaps you have a better reason
for turning the manifold over.

And how long is your leg now.........


"Drew Dalgleish" wrote in message
...
I took the mechanics word for it. It wasn't my motor and I didn't see
it in action . He did explain how and why he was doing it.

How did you measure the horsepower?

Roger

http://home.insightbb.com/~derbyrm

"Drew Dalgleish" wrote in message
...
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.

can I increase outboard hp?
 

Maybe an excuse to charge $75 per hour plus an additional fee for
"hotrodding" your o/b


"Drew Dalgleish" wrote in message
...
whatever you want to believe I guess. Perhaps you have a better reason
for turning the manifold over.

And how long is your leg now.........


"Drew Dalgleish" wrote in message
...
I took the mechanics word for it. It wasn't my motor and I didn't see
it in action . He did explain how and why he was doing it.

How did you measure the horsepower?

Roger

http://home.insightbb.com/~derbyrm

"Drew Dalgleish" wrote in message
.. .
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.

can I increase outboard hp?
 

On Sat, 24 Jun 2006 18:24:05 -0400, "John Cassara"
wrote:

Maybe an excuse to charge $75 per hour plus an additional fee for
"hotrodding" your o/b
Maybe but this guy works for $ 25 and I imagine that if the owner
didn't need a new prop he'd be ****ed

"Drew Dalgleish" wrote in message
...
whatever you want to believe I guess. Perhaps you have a better reason
for turning the manifold over.

And how long is your leg now.........


"Drew Dalgleish" wrote in message
...
I took the mechanics word for it. It wasn't my motor and I didn't see
it in action . He did explain how and why he was doing it.

How did you measure the horsepower?

Roger

http://home.insightbb.com/~derbyrm

"Drew Dalgleish" wrote in message
. ..
a few years ago I was shown how to turn a 5hp merc into an 8hp motor
just by nbolting the exhaust manifold rotating it 180 degrees and
reinstalling it.