How much change from 4 blade to 5 blade

[rphillips]

I have a 1997 19' BMC bass boat, heavy, but have no idea how many lbs. Mercury Black Max XR4 150hp eng. prop has no name nor # that I can find, it came from a prop shop in Nashville. I was told it was a 13" 24 pi. When taking off, the motor moans & strains for appx. 8 to 10 sec. before it plains off, then maxed out turns right near 5000rpm, just what the manual says it should turn. I have found a 5 blade 24pi High Five prop, for a reasonable $$. Could I expect very much difference in the hole shot or max rpm with this 5 blade compared to the 4 blade? I know there isn't a definite answer, but could I expect a noticeable difference or no difference at all? Thanks, Rick P.

 

[ondarvr]

It will most likely drop your RPMs and be slower on hole shot.

A 5 blade would typically have more blade area, so it would put more load on the motor, you would normally drop down in pitch when going with more blades.

​Your best bet would be to take the current prop to a shop that can tell what the pitch actually is, without that info there is no way to know what may work.

​What is the RPM range for your motor? you should be at the upper end with the average load in the boat.

 

[jimmbo]

The XR4 WOT range is 5000 - 5600 rpm, and it does prefer to be propped to run at the high end of the range

The High 5 blades are smaller than on 3 and 4 blade props, and the High 5 tends to have a smaller diameter. It is not known as a speed demon, but as prop very well suited for watersports