Just when I thought it was safe to buy a prop
 

The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j

Just when I thought it was safe to buy a prop
 

The difference between a 3 blade and 4 blade is...













wait for it....














DING!
1 blade more.

All things being equal(which they're not)the 4 blade takes more power to
turn for a given diameter and pitch. Thus, smaller Dia.

I went through the 4 blade thing a while back, couldn't see the case for
it to justify the expense then, or now.
JR

Josh Assing wrote:

The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j



--
--------------------------------------------------------------
Home Page: http://www.seanet.com/~jasonrnorth

Just when I thought it was safe to buy a prop
 

Josh Assing wrote:
The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j


If you don't need the additional surface area of a 4 blade, it is beyond
superfluous, it is a burden.

It sounds like you should stick with the 19P SS wheel. There are many
choices in that spec alone, even from just Quicksilver.

Rob

Just when I thought it was safe to buy a prop
 

On Wed, 25 Apr 2007 17:48:56 -0700, JR North
wrote:

I went through the 4 blade thing a while back, couldn't see the case for
it to justify the expense then, or now.

I had a different experience.

When I repowered with the ETEC, I used the recommended SS three blade
and had the exact same problem I had with the FICHT - no bow lift. The
boat just plowed until the engine got up to about 3k, then wham, it
was on plane.

I switched over to a same size/pitch four blade and big difference. I
had plenty of bite, bow lift up the wazoo and smooth acceleration.

Another problem solved by the four blade was cavitation. I've had that
problem with this boat for a long time in particular with certain
types of wave/wind conditions. When I switched to the four blade,
that problem also went away.

Since last summer, I've played with a couple of different 3 blade
props, but they just don't work as well as the four blade.

Just when I thought it was safe to buy a prop
 

I slip hard in turns -- as I understnad it; a 4 blade won't slip as much


On Wed, 25 Apr 2007 17:48:56 -0700, JR North
wrote:

The difference between a 3 blade and 4 blade is...













wait for it....














DING!
1 blade more.

All things being equal(which they're not)the 4 blade takes more power to
turn for a given diameter and pitch. Thus, smaller Dia.

I went through the 4 blade thing a while back, couldn't see the case for
it to justify the expense then, or now.
JR

Josh Assing wrote:

The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j

Just when I thought it was safe to buy a prop
 

19p isn't giving me the correct wot rpm range.


On Wed, 25 Apr 2007 21:29:36 -0400, trainfan1 wrote:

Josh Assing wrote:
The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j


If you don't need the additional surface area of a 4 blade, it is beyond
superfluous, it is a burden.

It sounds like you should stick with the 19P SS wheel. There are many
choices in that spec alone, even from just Quicksilver.

Rob

Just when I thought it was safe to buy a prop
 

Josh Assing wrote:
19p isn't giving me the correct wot rpm range.



That's an important piece of information you left out of your original
post. What are your numbers now? What boat/weight/engine/gear ratio?

Still, if you don't need the additional surface area of a 4 blade, it is
beyond superfluous.

It sounds like you should move to a quality 17P SS 3 blade wheel. The
prop design and your gear ratio will determine how much of a change will
occur.

Every prop is a compromise of sorts.

The most efficient prop is a one blade. They're a bear to balance, though.

2 blades are more efficient than 3, and are fine for very light planing
hulls(like hydros) that do not rely on a large surface area. Balancing
is still critical.

A 3 blade is a good compromise of surface area, balancing ease, weight,
& efficiency. 3 blade props have the widest choice of
shapes/profiles/cupping designs available.

4 & 5 blades are really specialty props for specific applications where
the extra surface area & ease of balancing are important, & weight is
not. The CNC'd 4 blade ski props, for example, are super-smooth &
quiet, and on a tournament hull very little if any top end is sacrificed.

A 4 blade can also help on certain planing hull designs where porpoising
is prevalent even with minimal trim-out.

You really need to know what your goal is in selecting a prop. The
ability to try several different styles would be a huge advantage. I
have one shop down in the Finger Lakes that has allowed me to do this
over the years.

Rob


On Wed, 25 Apr 2007 21:29:36 -0400, trainfan1 wrote:

Josh Assing wrote:
The local prop shop says that the Revolution4 (17 pitch) will yeild similar WOT
as my SS 3 blade (19 pitch) and recommended the apollo 4 blade SS in 16 pitch

That seems like a lot to drop -- and seems like it'd make my top end & midrange
suffer.

The mercury prop selector pushes the rev4 17; and I just can't find any other
prop-calculators...

They weren't too thrilled about me "trying the prop" and 'would have to get back
to me'

Thoughts on this mojo-prop-magic ?

-j

If you don't need the additional surface area of a 4 blade, it is beyond
superfluous, it is a burden.

It sounds like you should stick with the 19P SS wheel. There are many
choices in that spec alone, even from just Quicksilver.

Rob

Just when I thought it was safe to buy a prop
 

That's an important piece of information you left out of your original
post. What are your numbers now? What boat/weight/engine/gear ratio?

Blue water, unknown weight (heavy for hte size) 22' foot cuddy
350 GM engine (mercruiser)
1.47 ratio

4100 rpm at WOT, 45 mph in "perfect waters" (no chop, no wind, everything
trimmed to max it out w/o slip)

You really need to know what your goal is in selecting a prop. The
ability to try several different styles would be a huge advantage. I
have one shop down in the Finger Lakes that has allowed me to do this
over the years.

My goal is to maintain (or improve) fuel usage in mid-range cruisng (30mph or
so), and get on plane faster....

The "local" shop I use doesn't do loaners, havent' found one that will -- one
said "as long as you test it on the lakes, no salt water" the problem is that
is where I'm using the boat, so I need to test it in salt water ...


Thanks for your time.

Just when I thought it was safe to buy a prop
 

Josh Assing wrote:
That's an important piece of information you left out of your original
post. What are your numbers now? What boat/weight/engine/gear ratio?

Blue water, unknown weight (heavy for hte size) 22' foot cuddy
350 GM engine (mercruiser)
1.47 ratio

4100 rpm at WOT, 45 mph in "perfect waters" (no chop, no wind, everything
trimmed to max it out w/o slip)

You really need to know what your goal is in selecting a prop. The
ability to try several different styles would be a huge advantage. I
have one shop down in the Finger Lakes that has allowed me to do this
over the years.

My goal is to maintain (or improve) fuel usage in mid-range cruisng (30mph or
so), and get on plane faster....

The "local" shop I use doesn't do loaners, havent' found one that will -- one
said "as long as you test it on the lakes, no salt water" the problem is that
is where I'm using the boat, so I need to test it in salt water ...


Thanks for your time.


OK, I can't see going beyond a 17P SS 3 blade. Double cup, wide(er)
blades, maybe down 1/2" in diameter at most.

If you can get to a popular anchoring spot in season & strike up
conversations on props, you may find some folks who would like to try
your prop & your spare, and you theirs. I'm assuming your an
Alpha(drive), so there will plenty of those around.

Rob

Just when I thought it was safe to buy a prop
 

trainfan1 wrote:
Josh Assing wrote:

That's an important piece of information you left out of your
original post. What are your numbers now? What
boat/weight/engine/gear ratio?


Blue water, unknown weight (heavy for hte size) 22' foot cuddy
350 GM engine (mercruiser)
1.47 ratio

4100 rpm at WOT, 45 mph in "perfect waters" (no chop, no wind, everything
trimmed to max it out w/o slip)

You really need to know what your goal is in selecting a prop. The
ability to try several different styles would be a huge advantage. I
have one shop down in the Finger Lakes that has allowed me to do this
over the years.


My goal is to maintain (or improve) fuel usage in mid-range cruisng
(30mph or
so), and get on plane faster....

The "local" shop I use doesn't do loaners, havent' found one that will
-- one
said "as long as you test it on the lakes, no salt water" the
problem is that
is where I'm using the boat, so I need to test it in salt water ...


Thanks for your time.


OK, I can't see going beyond a 17P SS 3 blade. Double cup, wide(er)
blades, maybe down 1/2" in diameter at most.

If you can get to a popular anchoring spot in season & strike up
conversations on props, you may find some folks who would like to try
your prop & your spare, and you theirs. I'm assuming your an
Alpha(drive), so there will plenty of those around.

Rob

There use to be a program with Merc dealers to let you try props before
you buy them. They would paint the loaner props blue. I have no idea if
they still do it, but you might try asking around with merc dealers in
your area.

Capt Jack R..