I have 27 ft express, 7000 lbs, same power. I just ordered a stainless
steel 3 blade mirage plus 15.5 diameter by 15 pitch. Check out the mercury
marine website, there is a section you can input info for prop size
feedback. I did the same thing at Michigan Wheel (email them with required
info and they are to respond back) and never heard back. The merc prop is
about twice as much as the Michigan, hope it's worth it. Prior prop was a
Michigan SS 14.5 x 17 pitch (their recommendation). I never was quite
satified with that prop, not enough rpms on top end which seemed to impact
the hole shot when loaded down.
If you can find a dealer with the merc demo props give that a shot. Dealers
are listed on their web site.
Each boat seems a little different but I think it is worth the money to get
it right.
"Joseph Friess" wrote in message
.. .
I have a 1986 Searay Sundancer with a Mercruiser 350, 260HP, Alpha 1
sterndrive and boat weight of about 4700 lbs. I would be interested in the
prop size from any other owners of this size boat and engine.
Specifically,
what kind of speed to do get at 3000 rpm or 3500 rpm for a given prop
size.

With 2 adults, full tank of gas (70Gal) and water (30gal), I get around
19-21 mph at 3500 rpm with the outdrive and trim tabs optimized.This seems
a
bit slow for this rpm. I have a paddle wheel speedometer and GPS readings
and they are close, depending on the wind.

I don't know my prop size now, but will be getting it this week, weather
permitting. Any help or suggestions would be appreciated.