offshorefisher

I've always turned my bravo 2s outboard, but I'm thinking about swapping props. Aside from the manuevering changes, what else can I expect? Will this effect engine/drive loading? I've heard that I may get better efficiency, true?

monstaaa

usually turning in will increase speed,but not allways. gives more stern lift as well.

Darkspoilerzx

My experience has told me that the closer the drives are together the more difference it make on staggered engines it make a really big difference

deanpp

My 32 ft advantage runs and handles better turning IN

Illusive

Always think about where the clean water is, this is where the prop blade will take the strongest bite. Turning props in will help carry the bow, turning out will increase stern lift.

monstaaa

out is for bow lift and in is for stern lift.

each boat is different and should be tested with that in mind. most newer step bottom boats turn in , as most older straight bottom boats turn out. this is becaus of wetted surface. straight bottom needs more bow lift to release, and reduce wetted surface, were as steped bottoms naturally carry the bow due to inherent design thus inward turning carrying the stern.

JaayTeee

I wouldn't mess with it on a bravo 2 application.

I doub't you will see any performance increase, but you
will, for certain, notice poorer docking maneuvarability.

As for rotation and lift,
Inside ( starboard turning CCW, port CW)
produces bow lift, outside, stern lift.

Here's my theory on it.

Due to the angle of the V, the outside half
of the gearcase ( the side toward the chine)
has a higher percentage of water contact than the inside
of the gearcase( between the gearcase and keel)

With inside rotation, the blades are on the upswing in
the outside half of the rotation, the low pressure area
of the blade ( the front) is facing down, this will in effect,
drive downward, and increase trim leverage.
When the blade gets to the inside half of the rotation,
due to the V angle, it doesn't reach any solid water til
about the last third of the rotation, so the upward
lift the blades produce in that half of the rotatation
is minimal.

Outside rotation, the blades are on the downswing,
in the outside half of the rotation,
the low pressure area of the blade is facing up, the blade
is pushing water back, and down, trying to lift itself toward the surface
(stern lift).
The inside half of the swing suffers the same problem as noted previously,
(not enough solid water to dig in to)

Here's a simple test.
Take an oar, stick it straight down in the water, pitch it at a 45* angle, now try to
lift it to the surface in as if it were a prop blade in part of it's rotation cycle
Now, take the oar, lay it right atop the water at the
same 45* pitch, now , try to push it down to the bottom as if it were a prop blade
in a part of it's rotation cylcle.


You can get an idea of what wants to dig, and what wants to lift.

My boat runs inside rotation( straight v) and is a litle over 1 mph faster that way.

The Sh*tty handling of inside rotation is a whole nother chapter,
but involves the V, and, when in reverse, the thrust being thrown up
against the V, and pooling up, instead of going underneath the hull.

That's the way I see it.

Illusive

JaayTeee is right on with my experience.

rssteiny

so to try this you run both drives in reverse i assume, and that dont hurt anything??

monstaaa

no, bravos can turn either rotation.



and as stated earlier turning in gives stern lift. out bow lift.

this is not theory but fact.

not once but many,,,,,, many ,,,, rigs later.

such as this one.