When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray EC, I
occasionally experience what I think is cavitation when encountering rough
or choppy water at speeds around 35 mph. To get out of this condition,
adjusting the trim has little effect and sometimes it is necessary to come
off plane. I know there are some devises that can be attached to the
outdrive to help with this. Does anyone have any experience with this that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase in RPM and a
decrease in speed and is caused by the prop is not making proper contact
with the water, due to too much air around it.

There comes a point, where the conditions and your boat, don't match,
and you just have to slow down. You might be able to find some
doo-hickey, that will extend this point, but you need to decide if it's
worth it, for wear and tear on your equipment and yourself and passengers.
BG There's nothing wrong with going slow on the water ..... I've been
doing it for years ..... EG course, there's something to be said for
driving at the limits through a nasty head sea.......

otn

Jim Irvine wrote:

When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray EC, I
occasionally experience what I think is cavitation when encountering rough
or choppy water at speeds around 35 mph. To get out of this condition,
adjusting the trim has little effect and sometimes it is necessary to come
off plane. I know there are some devises that can be attached to the
outdrive to help with this. Does anyone have any experience with this that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase in RPM and a
decrease in speed and is caused by the prop is not making proper contact
with the water, due to too much air around it.

GO get a StingRay XP hydrofoil !
Solved many problems with that, and believe it or not , i have used that
equipment on many boat, and every time fuel consumption went down ! I'd say
a good 10 %
Good luck
"Jim Irvine" a écrit dans le message de news:
...
When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray EC, I
occasionally experience what I think is cavitation when encountering rough
or choppy water at speeds around 35 mph. To get out of this condition,
adjusting the trim has little effect and sometimes it is necessary to come
off plane. I know there are some devises that can be attached to the
outdrive to help with this. Does anyone have any experience with this
that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase in RPM and a
decrease in speed and is caused by the prop is not making proper contact
with the water, due to too much air around it.

On Fri, 8 Aug 2003 20:28:49 -0400, "Jim Irvine"
wrote:

When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray EC, I
occasionally experience what I think is cavitation when encountering rough
or choppy water at speeds around 35 mph. To get out of this condition,
adjusting the trim has little effect and sometimes it is necessary to come
off plane. I know there are some devises that can be attached to the
outdrive to help with this. Does anyone have any experience with this that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase in RPM and a
decrease in speed and is caused by the prop is not making proper contact
with the water, due to too much air around it.



Just so we're all talking about the same thing Jim:

Cavitation is the boiling and condensing of water vapor on the surface
of the prop. Can be very damaging to the prop, as it erodes the prop
metal.

Ventilation is the "sucking" of air into the prop area, causing a loss
of power, and increase in RPM's.

Here's a good "starter" link:
http://www.ribmagazine.com/propellers.htm

If you are ventilating your prop, there are a few remedies:
1.) slow down )
2.) adjust the motor height (down)
3.) try a "doelphin", or similar fin to reduce the induction of air.
4.) probably most important, make sure you have the right prop for
your boat.

Good luck,
noah


Courtesy of Lee Yeaton,
See the boats of rec.boats
www.TheBayGuide.com/rec.boats

Thanks for the clarification and it does sound more like ventilation. I'm
also wondering if trim tab setting can have anything to do with the
condition.

Or, maybe it would be best to stop making this more complicated than it is
and just slow the F___ down when it occurs - Doh!


"noah" wrote in message
...
On Fri, 8 Aug 2003 20:28:49 -0400, "Jim Irvine"
wrote:

When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray EC, I
occasionally experience what I think is cavitation when encountering
rough
or choppy water at speeds around 35 mph. To get out of this condition,
adjusting the trim has little effect and sometimes it is necessary to
come
off plane. I know there are some devises that can be attached to the
outdrive to help with this. Does anyone have any experience with this
that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase in RPM and a
decrease in speed and is caused by the prop is not making proper contact
with the water, due to too much air around it.



Just so we're all talking about the same thing Jim:

Cavitation is the boiling and condensing of water vapor on the surface
of the prop. Can be very damaging to the prop, as it erodes the prop
metal.

Ventilation is the "sucking" of air into the prop area, causing a loss
of power, and increase in RPM's.

Here's a good "starter" link:
http://www.ribmagazine.com/propellers.htm

If you are ventilating your prop, there are a few remedies:
1.) slow down )
2.) adjust the motor height (down)
3.) try a "doelphin", or similar fin to reduce the induction of air.
4.) probably most important, make sure you have the right prop for
your boat.

Good luck,
noah


Courtesy of Lee Yeaton,
See the boats of rec.boats
www.TheBayGuide.com/rec.boats

On Fri, 8 Aug 2003 23:17:49 -0400, "Jim Irvine"
wrote:

Thanks for the clarification and it does sound more like ventilation. I'm
also wondering if trim tab setting can have anything to do with the
condition.

Or, maybe it would be best to stop making this more complicated than it is
and just slow the F___ down when it occurs - Doh!


"noah" wrote in message
.. .
On Fri, 8 Aug 2003 20:28:49 -0400, "Jim Irvine"
wrote:

When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray EC, I
occasionally experience what I think is cavitation when encountering
rough
or choppy water at speeds around 35 mph. To get out of this condition,
adjusting the trim has little effect and sometimes it is necessary to
come
off plane. I know there are some devises that can be attached to the
outdrive to help with this. Does anyone have any experience with this
that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase in RPM and a
decrease in speed and is caused by the prop is not making proper contact
with the water, due to too much air around it.



Just so we're all talking about the same thing Jim:

Cavitation is the boiling and condensing of water vapor on the surface
of the prop. Can be very damaging to the prop, as it erodes the prop
metal.

Ventilation is the "sucking" of air into the prop area, causing a loss
of power, and increase in RPM's.

Here's a good "starter" link:
http://www.ribmagazine.com/propellers.htm

If you are ventilating your prop, there are a few remedies:
1.) slow down )
2.) adjust the motor height (down)
3.) try a "doelphin", or similar fin to reduce the induction of air.
4.) probably most important, make sure you have the right prop for
your boat.

Good luck,
noah


Courtesy of Lee Yeaton,
See the boats of rec.boats
www.TheBayGuide.com/rec.boats


Trim might have a small effect, but you'd have to raise the bow, which
is something not usually done in rough water.

If your engine sits "a little high", a doelphin or similar might help
significantly. I use one on my boat, and I get a quicker plane,
better fuel economy, and no noticeable loss of top end. Since they
are larger than the anti-ventilation plate on the leg, they also help
reduce ventilation.

Good luck,
noah

Courtesy of Lee Yeaton,
See the boats of rec.boats
www.TheBayGuide.com/rec.boats

I do not agree with the SS Prop at all. A SS Prop is
probably the worst thing you can put on your stern drive. If
you hit something in the water the prop will no give like an
alum. will and it causes a lot of shock on the lower unit
gears. SS no good. The boat hull design has a lot to do with
the performance and cavitation. It may be a problem you just
might have to live with.
"Jim Irvine" wrote in message
...
When cruising with my merc 5.0 alpha 1 on my 22 ft Sea Ray
EC, I
occasionally experience what I think is cavitation when
encountering rough
or choppy water at speeds around 35 mph. To get out of this
condition,
adjusting the trim has little effect and sometimes it is
necessary to come
off plane. I know there are some devises that can be
attached to the
outdrive to help with this. Does anyone have any experience
with this that
could perhaps recommend a solution?

When I refer to cavitation, the condition causes an increase
in RPM and a
decrease in speed and is caused by the prop is not making
proper contact
with the water, due to too much air around it.

If you hit something that hard in the parallel direction it is probably a
rock or a stump. In this case the skeg would hit first. The motor should
raise up and over. If you hit hard enough to damage, you would tear the
skeg off and have more damage than just the prop shaft and gears due to the
prop being SS. Probably the whole lower unit would be tore up. However,
anything is possible (like you could fall over w/ a heart attack while
reading this).

I look at the boat and prop from a performance point of view. Most people
want the most performance (either hole shot, acceleration, planing ability,
top speed, or something) they can get. If you are so concerned about damage
to the boat that you want to us an aluminum prop as a protector for your
motor, you need to invest in a good depth finder and learn the river. And
buy insurance on your boat. Insurance will be less than constantly
repairing/replacing aluminum props from sticks in the river that peel blades
off.


Tony
My boats and autos - http://t.thomas.home.mchsi.com



"Dean" wrote in message
...
Obviously you both have taken the extremes.

The prop hub shears during a perpendicular to the propshaft strike
(IE, when the face of one of the blades strikes a rock or log).

The propshaft will bend if you hit something and the force is parallel
to the propshaft. The hub will NOT protect from this type of damage.

An aluminum prop will break in the 2nd instance, whereas a SS quite
possibly won't.


-Dean

On Sat, 9 Aug 2003 20:42:16 -0500, "Boots Crofoot"
wrote:

I hate to tell you but you are. I use to work for Mercury
Marine. Have a great summer

--
http://ripperd2.dhs.org