Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Selecting Propeller for 40 HP Force
Posted by Can_38 on 07/04/13 - 11:56 AM
#1
Prop on my 1994 Force 40hp outboard is dinged up pretty bad and I'd like to replace it. How does one choose a correct fitting prop? And lastly youtube seems to make this job a simple DIY driveway project, true?
Edited by Tom W Clark on 07/04/13 - 7:25 PM
Posted by Tom W Clark on 07/04/13 - 7:24 PM
#2
Selecting a propeller can be a complex task or an easy task. It depends on a great number of things.
If the boat and motor are a popular combination, you can just see what others are using. Small boat have fewer options so that simplifies things even further. Large multi-engine boats with less common motors can be more difficult and large outboards have dozens and dozens of different propeller models to choose form.
In your case, a Force 40 is probably not on a very large boat, though you don't say, and the choices are not that great.
I know a Force 40 uses a small gearcase (3.5" propeller) but we need to know the recommended WOT operating engine speed range f that motor as well as the gear ratio of the gearcase. That information is in you Owner's Manual.
We also need to know how fast the bat can go. With that information, we can figure out the correct pitch of whatever model of propellers seems appropriate.
Changing a propeller is a very simple and easy task.
Posted by Can_38 on 07/05/13 - 11:41 AM
#3
1968 13' sport. Have only GPS my speed at 3/4 throttle = 20 mph. I don't have my outboard manual to answer your other questions.
Posted by Tom W Clark on 07/05/13 - 12:50 PM
#4
Remove the spark plugs, shift it into forward and rotate the flywheel by hand exactly twice. See how much the propeller rotates.
If it has a 2:1 gear ratio, the propeller will rotate exactly once.
If it has a 1.83:1 ratio it will rotate a little more than once.
Those are the two most likely ratios.
How many cylinders does it have?
Posted by Tom W Clark on 07/05/13 - 12:53 PM
#5
How do you know your Force is a 1994 model?
Does it have through-hub exhaust or not?
Posted by Tom W Clark on 07/06/13 - 5:37 AM
#7
Depends on if it's a 1994 or not, which is why I asked.
Posted by Binkie on 07/06/13 - 9:28 AM
#8
Thru hub exhaust started in 1995. On the above site, the engine serial number .determine the year. Easy for him to figure out.
Just trying to help.
Posted by Can_38 on 07/14/13 - 11:41 AM
#9
Tom W Clark wrote:
How do you know your Force is a 1994 model?
Does it have through-hub exhaust or not?
Sorry I let this slip. It's a non thru hub exhaust.