You really need to install a tach. Best money you will ever spend on your
boat. Will allow you to pick the right prop now. Will allow you to
diagnose any problems in the future.
Bottom line - a must for any boat to know what is going on.

No way to know if the boat is running right or not based on your post. But,
your old 35 vs a new 40 is not going to compare.
A 60 on a 16' will run 32 mph on gps. Not much difference in weight to be
honest. The 35 is just not much power.

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



"Jason" wrote in message
...
dont have a way to check RPM's unfortunatly... i found the id# finally on
the web, 10 1/2 inch, 13 pitch, seems to be right about in the middle for
sizes that will fit..

thanks!

"Wayne.B" wrote in message
...
On Wed, 20 Aug 2003 20:19:29 -0500, "Jason"
wrote:
Im questioning whether or not I have the correct prop on my outboard. I
purchased the boat used about a month ago. Its a 15' starcraft aluminum
boat
with a 35 hp mercury (1985). Im confident that the outboard is tuned
and
running well. I am getting about 22 mph (GPS) with two people onboard.
I
never questioned the speed until I went on a friends 24 ' pontoon boat
with
a 40hp motor and got to 18mph with 2 people on board. The weight
difference
has to be huge in the two boats.

On my prop it has the following markings :
48 816704 A40 13P

I've looked on google for any info but have come up dry. Can anyone
offer
any insight or am I running as can be expected.

22 MPH sounds about right to me for that boat/motor combination. When
I was a kid 35 HP motors were very common on 14 ft runabouts and we
used to get speeds in the low to mid 20s depending on the weight of
the boat. The only way to tell for sure is to check your RPMs at wide
open throttle and see where you are in the power curve.