All depends. A 3 blade prop will almost always be faster at top end than a
4 blade prop due to the decrease in blade surface. However, a 4 blade prop
will almost always plane faster and give better acceleration (assuming we
are talking about similar props in terms of design and similar pitch).
Having said that, in theory they will both be about the same economy wise at
say 3000 rpms since they are both the same pitch and about the same
efficiency wise in the mid rpm area.
Each person has to decide if they want better low end or better top end.
There is no perfect combination. Even the shift props will be less
efficient on top end than a regular prop of the same pitch. Again, you
compromise absolute top speed for acceleration. Just like gearing in a car.

Now for trim tabs. Great for slow planing but will kill fuel economy doing
so. They create a lot of drag to force the bow down at slower speeds. Of
course you can raise them and get the efficiency back. Dolfins work the
same way by forcing the bow down (not as much as a trim tab but it does
help). You just have to trim the motor out to stop the bow push. Of course
you always get some push since it is in the water unless you have the engine
raised to the point that it is out of the water at higher speeds.

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



"F330 GT" wrote in message
...
Hey Barry

I am basically am looking to be able to plain at a slower speed than I am
currently achieving. My boat doesnt like to hold a plain at under 25mph,
and
when it gets rough, I'd like to go slower than bouncing from one wave to
another. And yes I am also looking to maximize my range.

Thank you all, I appreciate your inputs...

Rick








Rick,

Sounds like trim tabs would do more for you than changing props. Their is
probably no better way to achieve slower planing speed than good trim
tabs. Of
course, that certainly won't be the most economical speed. Most new
outboards
are most economical in the 3500 to 4000 rpm range.

At certain rpm ranges, I imagine a 4 blade could be more economical than a
3
blade but I'd still be real surprised if you took an outboard motor on a
typical v-hull boat and tried just to maximize the most mileage per gallon
possible that could be gotten out of that engine, a 3 blade prop would be
the
winner.

What do you think, Tony?

Barry