You are correct Mike. For max top end speed you want to prop with a good
performance SS prop at about 300 rpms below max rated. This will give you
the best top speed but will hurt your hole shot some.

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

"MikeG" wrote in message
ews.com...
In article xcgQc.246823$XM6.7643@attbi_s53, says...
A 4 blade prop of the same pitch will be slower on top end due to the
extra
blade surface (althought a 4 blade will usually be smaller in diameter
to
help compensate - it still will be slower on top end).
A 4 blade prop of the same pitch will be faster out of the hole due to
less
slippage. A 4 blade is more efficient at lower rpms.

If your not comparing same pitch then all bets are off.




Ok then, if I understand this properly, if my main interest is strictly
fishing and towing a joy rider is only the faintest of possibilities and
assuming the same pith I'd be better served by a three bladed prop since
good hole shots are not a necessity but getting from one spot to another
in the fastest most efficient way would be?

Thanks again for the info.
--
MikeG
Heirloom Woods
www.heirloom-woods.net

Don't know what boat you have James but Turning a 5.7 at 5200 rpms for 4 or
5 minutes at a time will destroy the engine. Don't expect it to last more
than a couple of seasons if that long.

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

"JamesgangNC" wrote in message
k.net...
That must be a pretty heavy boat. Try going back to the 17. You might
even
want to try a 15. Personally I prefer to run the wot rpm a little high to
improve the hole shot. After all you can control how long you run it wide
open. I let my 5.7 turn about 5200 but seldom keep it there for more that
4
or 5 minutes.

"Joseph Stachyra" wrote in message
...
I keep telling people, 4 blade props will slow you down, and nobody
listens.....
go back to a 17" three blade, or check with a boat dealer what the
original
prop was....
if you want to push a 4 blade, then go to a 250 hp outboard.

"Shawn Willden" wrote in message
...
I have a 20' Bayliner, a 1990 with a 5.0L Merc and (I think) Alpha 1
outdrive. The engine has been modified with a 4BBL carb (now a marine
one,
for those who followed my earlier travails!) which should give it
about
230
HP (as comared with 200HP with the original 2BBL).

After getting the engine fixed up with the right kind of carb, I took
it
out
on the lake last week and while the engine seems to run well, there's
absolutely no way the boat could have gotten an adult out of the water
on
skis. Top speed is pretty good (nearly 40 mph, and this is at an
elevation
of over 5000 feet) but the boat is really slow to dig its way up onto
plane. As you might guess from the subject line, I suspect the prop.

This boat apparently came with, and was pretty much always run with, a
three-bladed 17 pitch prop. This spring, however, the former owner
trashed
the prop on a sand bar. Before he sold it, he purchased a new
four-bladed,
19 pitch aluminum prop (don't know what the diameter is, but it looks
about
the same as the previous 17-pitch prop, which he left in the boat).
My
suspicion is that this prop is just too much for my engine to turn,
but
I
don't really know if 2 inches of pitch make that much difference.

At plane, with a wide-open throttle (assuming the throttle cable is
adjusted
correctly), the engine peaks out at 3500 rpm. According to a
Mercruiser
manual I have, it should run to about 4200 WOT.

So, before I go buy a prop, what do you all think? Should this engine
be
able to handle a 19 pitch? Actually, I'll buy a prop anyway, because
it's
cheaper than looking into deeper engine problems, and if it gets me
acceptable performance, I'll stick with it. However, if the current
performance indicates that there might be other problems, I'd rather
know
sooner rather than later, even if I decide not to do anything.

Thanks for any help,

Shawn

In article hthQc.90165$eM2.6306@attbi_s51, says...
You are correct Mike. For max top end speed you want to prop with a good
performance SS prop at about 300 rpms below max rated. This will give you
the best top speed but will hurt your hole shot some.


Thank you much for clearing that up for me.

Would it be too much to hope that engine makers have charts available
that would indicate what can be expected from a particular engine/prop
(pitch) combination or is it a matter of asking the right people?

I have every intention of having a boat and having it in the water by
May 2005 at the latest. I've got a short list of requirements I want for
the 1 - the ideal boat 2- the practical ideal boat 3- the totally
practical boat.

The one area I'm still fuzzy on is the engine/prop relationship.
Unfortunately I haven't found much written material on the subject.
You've helped clear up quite a bit of that though.

Thanks
Mike

--
MikeG
Heirloom Woods
www.heirloom-woods.net

"Shawn Willden" wrote in message
...


My
suspicion is that this prop is just too much for my engine to turn, but I
don't really know if 2 inches of pitch make that much difference.

2 inches of pitch would make a BIG difference


At plane, with a wide-open throttle (assuming the throttle cable is
adjusted
correctly), the engine peaks out at 3500 rpm.

No question about it, you are running too much pitch. At 3500 RPM your
engine is probably only producing about 60% of its rated horsepower. I am
guessing that your hole shot has the RPMs down in the low 2000 range, at
which point your engine is only producing about 1/3 of its rated horsepower.

You need more RPMs from the engine!


So, before I go buy a prop, what do you all think?

I think that you should "try before you buy".

Many of the boat shops carry loaner props for exactly this reason. Some
rent the props, then apply the rental to a purchase. Others just take a
security deposit and loan them out.

Call the shops in your area and see what is available. If you can take two
or three at a time spend a few hours test driving props. Put a prop on,
launch, take a few quick passes, come back and repeat. Once you settle on a
prop, buy it! And buy it from the shop that provided you this service, not
the cheapest online place you can find!


Rod

It is really a matter of trial and trial and trial depending on your rig and
how you run it. The best prop for me with 1 person in my boat will not be
the best for you if you always have 3 people in the boat.

The manufacturer will get you in the right area in terms of pitch but you
have to decide from there how you want the boat to perform and with what
load and at what rpm.


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

"MikeG" wrote in message
ews.com...
In article hthQc.90165$eM2.6306@attbi_s51, says...
You are correct Mike. For max top end speed you want to prop with a
good
performance SS prop at about 300 rpms below max rated. This will give
you
the best top speed but will hurt your hole shot some.


Thank you much for clearing that up for me.

Would it be too much to hope that engine makers have charts available
that would indicate what can be expected from a particular engine/prop
(pitch) combination or is it a matter of asking the right people?

I have every intention of having a boat and having it in the water by
May 2005 at the latest. I've got a short list of requirements I want for
the 1 - the ideal boat 2- the practical ideal boat 3- the totally
practical boat.

The one area I'm still fuzzy on is the engine/prop relationship.
Unfortunately I haven't found much written material on the subject.
You've helped clear up quite a bit of that though.

Thanks
Mike

--
MikeG
Heirloom Woods
www.heirloom-woods.net

Depends on the engine :-) Late model 1 ton truck block, 4 bolt main, chevy
pink rods, keith black pistons, crane roller cam and roller rockers,
edlebrock performer rpm aluminum heads and aluminum intake.

"Tony Thomas" wrote in message
news:muhQc.90170$eM2.58740@attbi_s51...
Don't know what boat you have James but Turning a 5.7 at 5200 rpms for 4
or
5 minutes at a time will destroy the engine. Don't expect it to last more
than a couple of seasons if that long.

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

"JamesgangNC" wrote in message
k.net...
That must be a pretty heavy boat. Try going back to the 17. You might
even
want to try a 15. Personally I prefer to run the wot rpm a little high
to
improve the hole shot. After all you can control how long you run it
wide
open. I let my 5.7 turn about 5200 but seldom keep it there for more
that
4
or 5 minutes.

"Joseph Stachyra" wrote in message
...
I keep telling people, 4 blade props will slow you down, and nobody
listens.....
go back to a 17" three blade, or check with a boat dealer what the
original
prop was....
if you want to push a 4 blade, then go to a 250 hp outboard.

"Shawn Willden" wrote in message
...
I have a 20' Bayliner, a 1990 with a 5.0L Merc and (I think) Alpha 1
outdrive. The engine has been modified with a 4BBL carb (now a
marine
one,
for those who followed my earlier travails!) which should give it
about
230
HP (as comared with 200HP with the original 2BBL).

After getting the engine fixed up with the right kind of carb, I
took
it
out
on the lake last week and while the engine seems to run well,
there's
absolutely no way the boat could have gotten an adult out of the
water
on
skis. Top speed is pretty good (nearly 40 mph, and this is at an
elevation
of over 5000 feet) but the boat is really slow to dig its way up
onto
plane. As you might guess from the subject line, I suspect the
prop.

This boat apparently came with, and was pretty much always run with,
a
three-bladed 17 pitch prop. This spring, however, the former owner
trashed
the prop on a sand bar. Before he sold it, he purchased a new
four-bladed,
19 pitch aluminum prop (don't know what the diameter is, but it
looks
about
the same as the previous 17-pitch prop, which he left in the boat).
My
suspicion is that this prop is just too much for my engine to turn,
but
I
don't really know if 2 inches of pitch make that much difference.

At plane, with a wide-open throttle (assuming the throttle cable is
adjusted
correctly), the engine peaks out at 3500 rpm. According to a
Mercruiser
manual I have, it should run to about 4200 WOT.

So, before I go buy a prop, what do you all think? Should this
engine
be
able to handle a 19 pitch? Actually, I'll buy a prop anyway,
because
it's
cheaper than looking into deeper engine problems, and if it gets me
acceptable performance, I'll stick with it. However, if the current
performance indicates that there might be other problems, I'd rather
know
sooner rather than later, even if I decide not to do anything.

Thanks for any help,

Shawn

I owned a 89 Scarab with 5.7l Chevy/Merc engine and had it propped to turn
5000rpm. 10 years later when I sold the boat it still was running strong as
new.

"Tony Thomas" wrote in message
news:muhQc.90170$eM2.58740@attbi_s51...
Don't know what boat you have James but Turning a 5.7 at 5200 rpms for 4
or
5 minutes at a time will destroy the engine. Don't expect it to last more
than a couple of seasons if that long.

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

"JamesgangNC" wrote in message
k.net...
That must be a pretty heavy boat. Try going back to the 17. You might
even
want to try a 15. Personally I prefer to run the wot rpm a little high
to
improve the hole shot. After all you can control how long you run it
wide
open. I let my 5.7 turn about 5200 but seldom keep it there for more
that
4
or 5 minutes.

"Joseph Stachyra" wrote in message
...
I keep telling people, 4 blade props will slow you down, and nobody
listens.....
go back to a 17" three blade, or check with a boat dealer what the
original
prop was....
if you want to push a 4 blade, then go to a 250 hp outboard.

"Shawn Willden" wrote in message
...
I have a 20' Bayliner, a 1990 with a 5.0L Merc and (I think) Alpha 1
outdrive. The engine has been modified with a 4BBL carb (now a
marine
one,
for those who followed my earlier travails!) which should give it
about
230
HP (as comared with 200HP with the original 2BBL).

After getting the engine fixed up with the right kind of carb, I
took
it
out
on the lake last week and while the engine seems to run well,
there's
absolutely no way the boat could have gotten an adult out of the
water
on
skis. Top speed is pretty good (nearly 40 mph, and this is at an
elevation
of over 5000 feet) but the boat is really slow to dig its way up
onto
plane. As you might guess from the subject line, I suspect the
prop.

This boat apparently came with, and was pretty much always run with,
a
three-bladed 17 pitch prop. This spring, however, the former owner
trashed
the prop on a sand bar. Before he sold it, he purchased a new
four-bladed,
19 pitch aluminum prop (don't know what the diameter is, but it
looks
about
the same as the previous 17-pitch prop, which he left in the boat).
My
suspicion is that this prop is just too much for my engine to turn,
but
I
don't really know if 2 inches of pitch make that much difference.

At plane, with a wide-open throttle (assuming the throttle cable is
adjusted
correctly), the engine peaks out at 3500 rpm. According to a
Mercruiser
manual I have, it should run to about 4200 WOT.

So, before I go buy a prop, what do you all think? Should this
engine
be
able to handle a 19 pitch? Actually, I'll buy a prop anyway,
because
it's
cheaper than looking into deeper engine problems, and if it gets me
acceptable performance, I'll stick with it. However, if the current
performance indicates that there might be other problems, I'd rather
know
sooner rather than later, even if I decide not to do anything.

Thanks for any help,

Shawn