I didn't see anyone disputing that.

"Woodchuck" wrote in message
.. .
Tony, don't sound like anyone believes you with the 15hp = 1mph faster! I
do!


"tony thomas" wrote in message
news:PiKpe.27752$x96.17450@attbi_s72...
Unless you are rebuilding the engine anyway, I would not waist my money.
It takes a lot of hp to gain any real benefit on the water. Most quote
15 hp to 1 mph. Spend your money on a 350 assuming your boat is 18' or
bigger. A 17' will probably run sideways from the torque.

Biggest bang for the buck is usually found by going to a good performance
SS prop. You can see 5 mph gain with the right prop over a cheap
aluminum one.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Gorf" wrote in message
...
I have done some research and heard you can put higher compression
flat-top
pistons in the 4.3 and gain a few HP. Who makes these pistons? I have
done a
bunch of searches and come up empty handed.

A related question, I have also read that the 4.3 is a 350 minus two
cylinders and that the pistons and rods are the same. Is this true or
false?




--
John

WWW.Firewalk-NC.com

"Be the change you wish to see in others"

----Gandhi

I will. I added 15 hp to one of my boats and more than doubled my
speed. 9.8 HP outboard = 7~8 mph I switched to a 25 HP = 20~25MPH
depending on load. 15HP increase = 13~17MPH speed increase. on an 16'6"
aluminum boat.

Paul

JamesgangNC wrote:
I didn't see anyone disputing that.

"Woodchuck" wrote in message
.. .
Tony, don't sound like anyone believes you with the 15hp = 1mph faster! I
do!


"tony thomas" wrote in message
news:PiKpe.27752$x96.17450@attbi_s72...
Unless you are rebuilding the engine anyway, I would not waist my money.
It takes a lot of hp to gain any real benefit on the water. Most quote
15 hp to 1 mph. Spend your money on a 350 assuming your boat is 18' or
bigger. A 17' will probably run sideways from the torque.

Biggest bang for the buck is usually found by going to a good performance
SS prop. You can see 5 mph gain with the right prop over a cheap
aluminum one.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Gorf" wrote in message
...
I have done some research and heard you can put higher compression
flat-top
pistons in the 4.3 and gain a few HP. Who makes these pistons? I have
done a
bunch of searches and come up empty handed.

A related question, I have also read that the 4.3 is a 350 minus two
cylinders and that the pistons and rods are the same. Is this true or
false?




--
John

WWW.Firewalk-NC.com

"Be the change you wish to see in others"

----Gandhi

Probably enough power to get the boat to plane. Displacement speed before.
Bill

"Paul" wrote in message
oups.com...
I will. I added 15 hp to one of my boats and more than doubled my
speed. 9.8 HP outboard = 7~8 mph I switched to a 25 HP = 20~25MPH
depending on load. 15HP increase = 13~17MPH speed increase. on an 16'6"
aluminum boat.

Paul

JamesgangNC wrote:
I didn't see anyone disputing that.

"Woodchuck" wrote in message
.. .
Tony, don't sound like anyone believes you with the 15hp = 1mph faster!
I
do!


"tony thomas" wrote in message
news:PiKpe.27752$x96.17450@attbi_s72...
Unless you are rebuilding the engine anyway, I would not waist my
money.
It takes a lot of hp to gain any real benefit on the water. Most
quote
15 hp to 1 mph. Spend your money on a 350 assuming your boat is 18'
or
bigger. A 17' will probably run sideways from the torque.

Biggest bang for the buck is usually found by going to a good
performance
SS prop. You can see 5 mph gain with the right prop over a cheap
aluminum one.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Gorf" wrote in message
...
I have done some research and heard you can put higher compression
flat-top
pistons in the 4.3 and gain a few HP. Who makes these pistons? I have
done a
bunch of searches and come up empty handed.

A related question, I have also read that the 4.3 is a 350 minus two
cylinders and that the pistons and rods are the same. Is this true or
false?




--
John

WWW.Firewalk-NC.com

"Be the change you wish to see in others"

----Gandhi

Your talking about a 1.5 times increase in hp. We are talking about adding
15 hp to an engine that has 190 hp to begin with. Going from 190 to 205
will not increase the speed by 13~17 MPH. It may increase it by 2 mph if
your lucky.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Paul" wrote in message
oups.com...
I will. I added 15 hp to one of my boats and more than doubled my
speed. 9.8 HP outboard = 7~8 mph I switched to a 25 HP = 20~25MPH
depending on load. 15HP increase = 13~17MPH speed increase. on an 16'6"
aluminum boat.

Paul

JamesgangNC wrote:
I didn't see anyone disputing that.

"Woodchuck" wrote in message
.. .
Tony, don't sound like anyone believes you with the 15hp = 1mph faster!
I
do!


"tony thomas" wrote in message
news:PiKpe.27752$x96.17450@attbi_s72...
Unless you are rebuilding the engine anyway, I would not waist my
money.
It takes a lot of hp to gain any real benefit on the water. Most
quote
15 hp to 1 mph. Spend your money on a 350 assuming your boat is 18'
or
bigger. A 17' will probably run sideways from the torque.

Biggest bang for the buck is usually found by going to a good
performance
SS prop. You can see 5 mph gain with the right prop over a cheap
aluminum one.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Gorf" wrote in message
...
I have done some research and heard you can put higher compression
flat-top
pistons in the 4.3 and gain a few HP. Who makes these pistons? I have
done a
bunch of searches and come up empty handed.

A related question, I have also read that the 4.3 is a 350 minus two
cylinders and that the pistons and rods are the same. Is this true or
false?




--
John

WWW.Firewalk-NC.com

"Be the change you wish to see in others"

----Gandhi

But with that increase in HP you should be able to run a higher pitch
prop. A 2" pitch increase at a prop speed of 2500 rpms should give you
4.7 MPH speed increase. My 9.8 would never be able to get to WOT with a
13" prop on my boat. But the 25 HP has no problem. If you do get more
ponies from an engine upgrade. You should look at changing the prop. A
prop turning at a certain speed is only going to go so fast not matter
how much horse power is behind it.

Paul

You forgot to divide by the gear ratio. With a 1.87 gear and taking into
account an efficiency of 90% for a SS prop you get 2.2 MPH. But increasing
from 190 to 205 hp is probably not enough to increase by 2" of pitch on top
end. You could go 1" of pitch and get 1.1 MPH or the extra rpms w/ the same
pitch will give you the same.

Again - your comparing a 1500% increase to an increase of 8%. Don't come
close to being the same.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com

-
"Paul" wrote in message
ups.com...
But with that increase in HP you should be able to run a higher pitch
prop. A 2" pitch increase at a prop speed of 2500 rpms should give you
4.7 MPH speed increase. My 9.8 would never be able to get to WOT with a
13" prop on my boat. But the 25 HP has no problem. If you do get more
ponies from an engine upgrade. You should look at changing the prop. A
prop turning at a certain speed is only going to go so fast not matter
how much horse power is behind it.

Paul

The 2500 RPM was the prop speed. That would be 5000 RPM on the engine.
I accounted for the gear reduction. So a 2" pitch increase would give
you a 4.7 MPH increase. I know it is not a 100% efficient. And whether
or not the extra 15 HP can turn a 2" bigger prop 2500 RPM I do not
know. But if do several modifications that give you 15HP here, 5HP here
and 10HP there it all adds up. You can do headers, Fuel injection,
upgrade the ignition, camshaft, computer etc... The 4.3L motor is very
a versatile motor. I personally have seen (out of vehicle on a dyno) a
10 hp increase just by adding a spacer (a $100 item
http://www.jetchip.com/TBI/chevFSTBI.cfm) under a TBI unit on 4.3L
motor. I would put one on my Blazer but I would not be able to close
the hood. I have done a lot of work on the 4.3 in land vehicle
applications. Limited, but expanding, in boating applications.

Paul

You have to remember how many of these add-ons are advertised. They use the
word "up to" a lot. They may claim a 15hp increase but the results may only
be 2hp in real world. Granted the 4.3 can make some good power, but building
one for marine use is different than a car/truck. You need to build and
engine to make torque.

"Paul" wrote in message
ups.com...
The 2500 RPM was the prop speed. That would be 5000 RPM on the engine.
I accounted for the gear reduction. So a 2" pitch increase would give
you a 4.7 MPH increase. I know it is not a 100% efficient. And whether
or not the extra 15 HP can turn a 2" bigger prop 2500 RPM I do not
know. But if do several modifications that give you 15HP here, 5HP here
and 10HP there it all adds up. You can do headers, Fuel injection,
upgrade the ignition, camshaft, computer etc... The 4.3L motor is very
a versatile motor. I personally have seen (out of vehicle on a dyno) a
10 hp increase just by adding a spacer (a $100 item
http://www.jetchip.com/TBI/chevFSTBI.cfm) under a TBI unit on 4.3L
motor. I would put one on my Blazer but I would not be able to close
the hood. I have done a lot of work on the 4.3 in land vehicle
applications. Limited, but expanding, in boating applications.

Paul