Yamaha 55EL prop three or four blade ??

[jurgenscraft]

I am currently running a Yamah 55el with a three blade propellor, the choices I have at the moment are,11 1/2 x 12 and 11 1/2 x 13 pitch. what would be the advantages I would experience by changing to a four blade propellor and what would the equivalent propellor sizes and pitches be, another question I have is, of the two propellors I have the 12 inch and 13 inch pitch should have a difference of about 200 rpm,if this is the case why such a small difference in propellor size increments,surely blade shape would be of more importance, maybe this is a science all of it's own.( where on the web can I get more information regarding propellor design.

 

[walleyehed]

Re: Yamaha 55EL prop three or four blade ??

There are a gazillion sites from Prop manufacturers that give some decent info on what term means what...and what that application is used for, but most stop short of explaining enough to get you what you need to know.<br />In a 4blade, you will notice a slight increase in hole-shot, but at the cost of a small amount of top end. Vibration is less as well as steering torque<br />4blade is usually best suited to high HP, high engine heigth applications..<br />What in particular are you looking for in a prop???

 

[jurgenscraft]

Re: Yamaha 55EL prop three or four blade ??

hello Kenny, I need to drop the wot rpm by about 300 rpm<br />eliminate a bit of vibration at wot, the hole shot is okay but a improvement will also be welcome,I have been advised to add one of those fin things to the cavitation plate to improve ecenomy and performance, I would rather try a 4 blade propellor, what do you think. the boat handles very well as is, so I do not see the need for any stabilizers at this time,thank you for the reply, I look forward to receiving more informatiom on this forum,kind regards William Wright.

 

[walleyehed]

Re: Yamaha 55EL prop three or four blade ??

What prop are you using now, and what is the WOT RPM????

 

[jurgenscraft]

Re: Yamaha 55EL prop three or four blade ??

Walleyhed.<br />The propellors I have tried and find quite sucessefull are 11 1/2 x 12 pitch and 11 1/2 x 13 pitch the wot is 4500 to 5500 rpm what I am trying to find out is ?, what would the equivalent 4 blade propellors be in size and pitch ?,or would the also be 11 1/2 x 13 pitch but would there be four blade instead of three?, I seldomly run at wide open throttle normally around 3/4 throttle,or less,I run full throttle get onto the plane and then ease off the throttle and just stay on the plane.I was hoping that the four blade prop would help with the hole shot and save a small amount of fuel,<br />Kind Regards.Willie Wright.

 

[walleyehed]

Re: Yamaha 55EL prop three or four blade ??

In most cases, they do tend to have a better mid-range....<br />Diameter is usually a slight bit smaller on the 4-blade in the same pitch.<br />If the 12 pitch 3 blade puts you the closest to 5500, that should be a good choice in a 4-blade.