Based on what you use the boat I would suggest the following:

1. Install whale tail. This will help maintain plane at lower speeds.
2. Increase pitch to a 19. This will get your rpms down, increase top
speed, and increase effeciency by traveling more distance per rpm. You
obviously dont want to go below 4500 on top end and the 19 will put you at
about 5200.
3. Going to a 4 blade is a matter of choice. It will cost more to purchase
and repair. It will help on the acceleration. And will probably help on
the planing speed but not as much as the whale tail. In this case - I would
probably stay w/ the 3 blade.

As for SS. There is a rubber hub that will break free long before you tear
up the gears in the outdrive if all that hits is the prop. Small strikes -
you will never know you did w/ the SS and the aluminum will have the ear
tore off.
SS will also give you a little better performance as the blade design is
more efficient.

Bottom line - Whale Tail and a SS 3 blade 19 pitch. You won't believe the
difference.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
"MikeG" wrote in message
ews.com...

The basics.

I've got a 1985 seaway V hull that weighs in around 2k. It is powered by
an OMC 1.6 L seadrive. Full throttle range is listed as 4500 to 5500 RPM
and has a 13 1/4 X 17 three bladed prop on it. The prop's condition is
such that it has to be replaced come spring. I will, at some point, have
the existing one repaired and use it for a spare.

I fish. I don't foresee towing or pulling anything, skiers, float toys,
etc, behind the boat. While high speed is nice my main interest is
efficiency. Especially in fuel consumption and range.

As it sits the boat runs about 30MPH at 5500 RPM and falls off the plane
right around 20 MPH at 4600RPM. These figures may, considering the
condition of the present prop, improve slightly with a new prop of the
same size. I don't know that for sure though.

Looking at the figures it appears to me that, though I would like to be
able to maintain the plane down to about 17 MPH, this is about as good
as it gets for the boat/engine combination.

Is it? Would I be able to realize something more efficient with a
different prop, and, more importantly for making my decision, What
effects be if I were to change to a four blade and or change the pitch,
maybe even change the size if that is possible? Stainless steel is not
an option. I fish the rocky coast around Boston harbor and would rather
replace a prop rather then the lower end should I get stupid.

PLEASE, just comments on the matter at hand and try not to end up in an
infantile name calling contest of no value.

Thank you





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