RPMS at WOT

[gman2310]

I have a mercury bigfoot 60 on a 20 foot pontoon, the rams don't seem to get past 4100, does that sound right. It just feels like it should have a little more

 

[ondarvr]

No, that would be very low. I'm not sure what the RPM range is on that motor, but it's at least 1,000 more than that. Time for a different prop if the motor is running correctly.

 

[gman2310]

I actually changed the prop this year, I went with Mercs prop selector for the motor and size of boat, but it seems to be running slower than last prop

 

[ondarvr]

What size was the first one, and what size is this one, plus what were your RPM's and speed with each one?

 

[gman2310]

Numbers on old prop are 48. 77338. A4.5. 11 p don't remember rpms, new one is 13.4 diameter 15 pitch with 4100 wot. Also went from 3-4 blades

 

[ondarvr]

The old one was probably a better fit for your application, it was an 11, maybe a 12 would be good, the current one is a 15.

 

[Silvertip]

That is totally the wrong prop for a pontoon, for a big foot, and for a 20 footer. The proper prop is a 14 x 9P and if you are routinely running lightly loaded, a 14 x 11 might work.. There are pontoon specific props which are readily identifiable by their large rounded "elephant ears" looking blade shape. These props also provide better performance in reverse than a standard prop. This is especially important when docking or navigating in tight quarters.

 

[gman2310]

silver tip you have a part number of a prop I should use. The last time i selected the last prop, I used Mercs Prop Selector guide and thats what it suggested. Also, Do I stay with the 3 blade or 4 blade?

 

[ondarvr]

4 blade high thrust, but I don't have a number for you.