4 vs. 3 blade propeller

[Chuck S]

My Honda 50 came on the boat with a 3x11.1x13 propeller.

Honda (and my local dealer) has an available 4x10.6x13 propeller. Half an inch smaller diameter, same pitch, more blade surface.

Any reason to get or not get the 4 blade version?

My math tells me they're both going to run the same speeds since they're 13" pitch.

I need to have a spare propeller aboard, especially for the Ohio River.

Any advise appreciated!

-- Chuck

 

[KenMcC]

If a blade gets dinged, you have less imbalance if it is a four blade rather than a three blade. (25% as opposed to 33%).

The chances of damaging a blade if you hit something are probably pretty much equal with either prop, because one way or the other, if there is junk, you'll hit it, and unless it's real big junk, the prop will push it aside. Small junk and it's a one blade hit, big junk and you probably have a bigger problem anyway.

Unless there's a significant cost difference, I'd go for the four-blade prop. Might even add a little more efficiency while slow cruising.

Ken

 

[Chuck S]

Ken --

Thanks, I'm going to pick up the 4 blade and try her out on the local inland lake this week and see how she compares to the 3. One of 'em will become the spare is the 4-blade runs well.

I can run 6000 rpm with the 3 blade lightly loaded.

-- Chuck

 

[Sea Wolf]

Chuck- The four blade has more surface area than the three blade. This should give you slightly to moderately better acceleration out of the hole (less slippage), and a very small decrease in top end (more drag).

More important would be if one prop were cupped and the other not. A cupped prop acts like it has about an inch more pitch than it's rating, and has a wider useful range since the cupping acts like a variable pitch surface.

Better yet, the four blade prop should have less vibration with the extra blade, if they're both equally balanced. At the slowest speed in gear, you can often feel the vibration from individual blades turning, and it's sometimes especially apparent when turning the steering wheel with the "no feed back" cable lock released on a a Teleflex system.

My guess is that if the pitch/RPM is right on the 4 blade, you'll probably like it better. Let us know how it comes out. Joe.