Kurt Green
Lake Villa, IL
Boat Name: Sharon Lee
Model/Year: C22 / 1973
Hull No. 2162
Hailing Port: Great Lakes, IL |
 02/21/2004 4:49 AM Pacific Time
On my old two stroke 8hp Mariner I have a 9 x 6.25 prop.
I have no real complaints about it, but would like to hear from the learned
group whether this is an appropriate prop or not.
At low rpm I seem to have no problem with excessive thrust (for docking), and
at 'sweet spot' cruise I get 5 knots at .6 gallons per hour.
The full designation on the prop is NPC 9x6-1/4-C
Any thoughts?
Kurt Green
s/v Sharon Lee
C22 #2162 Great Lakes IL
http://hometown.aol.com/knights5/myhomepage/svsharonlee.html
|
Michael Smalter
Webster, NY
Boat Name: Marrakesh
Model/Year: 1986
Hull No. 13645
Hailing Port: Rochester, NY |
02/21/2004 11:22 AM Pacific Time
Your gas consumption sounds very good. I have an Evinrude 8 that uses about 1 gallon /hour at 6 knots. Top speed is about 6.5 knots. I don't knw the pitch of the prop. Is it stamped on the prop somewhere? |
Kurt Green
Lake Villa, IL
Boat Name: Sharon Lee
Model/Year: C22 / 1973
Hull No. 2162
Hailing Port: Great Lakes, IL |
02/22/2004 7:10 AM Pacific Time
The prop info was stamped on one of the blades.
I found that while at 5 knots I got .6 gph, it was interesting that at 5.5 knots I got 1.1 gph! |
Peter furness
chesapeake city, md 21915
Boat Name: More slack
Model/Year: 22 1986
Hull No. 14634
Hailing Port: town point, md. |
04/11/2005 5:11 PM Pacific Time
Kurt, Basically your engine will be the most efficient at 2/3 to3/4 throttle. Above that you may get more speed but you will consume much more fuel and create more wear and tare on the power plant |
Mike Bracket
Clinton Twp, MI
Boat Name: Gunsmoke
Model/Year: 1979
Hull No. 9150
Hailing Port: Lake St Clair MI |
04/30/2005 5:08 PM Pacific Time
Typically the motor will come from the factory with the "standard" prop, about the max diameter (first number) and the middle of the road pitch (second number) for that motor. If you are using the motor on a sailboat, you would like to have a bit less pitch (next lower number) to get the low end power from the motor. You will want to get the boat moving quickly, but as pointed out here, once you get to about 5.5 or 6 knots you are about as fast as you can go. More power uses more fuel for a minor improvement in speed.
A larger pitch will give you more top end speed but after about 6 or 6.5 it is mostly theoretical because all you will really notice is more fuel usage.
A smaller pitch also allows the motor to accelerate up to full throttle faster where it is most effective.
Mike Bracket |
