jjjansk
Active member
Finally had a chance to finish out the testing with the new props on the F150s (on a bracket) 2520DV PH. We switched from the Yamaha black steel 13.75X17 to the Powertech OFS 4 blades 15.25X15 and I have to say at first I was skeptical if the F150s would be able to spin those props. They are considerably bigger than the 3 blades. To my surprise they are a perfect swap as you can see from the numbers below. These numbers are done with the motors tucked all the way in to prevent there from being any variance in trim angle thus causing inaccurate comparison
RPM old props
2900 13.5 MPH
3400 19.7
3900 26.2
4400 31
4900 35.3
5200 37.2
motors trimmed out
6000 45.5
New Props
2900 15.8 MPH
3400 22
3900 26.8
4400 30.6
4900 34.1
5200 36.5
motors trimmed out
6000 42
New props motors raised one hole
2900 17 MPH
3400 23
3900 27.5
4400 31.2
4900 34
5200 37.3
motors trimmed out
6000 42
As you can see the new props performed better in the low RPM range due to less prop slip, as the speed increased the 3 blades catch up in performance. I did not even look at fuel burn as my main concern was speed at a given RPM and how the motor sounded. Most of our running here in the Gulf of Mexico is done in the 38-4400rpm range so the 4 blades will be just a tad more efficient. Our main reason for switching to 4 blades was to stop blowout in a following-quartering sea. If you do blow these out they immediately bite once trimmed down a little where the 3 blades required coming off plane and starting again. We moved the motors up one hole (just to see) I’m not sure as to how this will work, we have to run with the motors tucked a little deeper than level to the water line while on plane to prevent intermittent cavitation. This may be ok since running with the motors a little tucked brings the bow down and is still a bit more efficient than with the motors mounted in the btm hole and trimmed level. Hopefully the wind will stop blowing here in the next week or so and we will be able to make a run offshore and get some real world test results. Once we do this I will post again and give some feedback on performance.
Ok so here is my plug for Powertech and Nettle’s Props (Austin Texas). Nettle’s had the cheapest price I could find and he is on a first name basis with Marcus at Powertech. I had a few questions so JT at nettle’s conference called Marcus and they both spent 30+ minutes talking props and boat performance with me. Never once did Marcus push their prop over a competitor’s he just pushed 4 blades over 3. I highly recommend both companies and if you have any questions about props don’t hesitate calling Powertech they will answer any questions you have.
RPM old props
2900 13.5 MPH
3400 19.7
3900 26.2
4400 31
4900 35.3
5200 37.2
motors trimmed out
6000 45.5
New Props
2900 15.8 MPH
3400 22
3900 26.8
4400 30.6
4900 34.1
5200 36.5
motors trimmed out
6000 42
New props motors raised one hole
2900 17 MPH
3400 23
3900 27.5
4400 31.2
4900 34
5200 37.3
motors trimmed out
6000 42
As you can see the new props performed better in the low RPM range due to less prop slip, as the speed increased the 3 blades catch up in performance. I did not even look at fuel burn as my main concern was speed at a given RPM and how the motor sounded. Most of our running here in the Gulf of Mexico is done in the 38-4400rpm range so the 4 blades will be just a tad more efficient. Our main reason for switching to 4 blades was to stop blowout in a following-quartering sea. If you do blow these out they immediately bite once trimmed down a little where the 3 blades required coming off plane and starting again. We moved the motors up one hole (just to see) I’m not sure as to how this will work, we have to run with the motors tucked a little deeper than level to the water line while on plane to prevent intermittent cavitation. This may be ok since running with the motors a little tucked brings the bow down and is still a bit more efficient than with the motors mounted in the btm hole and trimmed level. Hopefully the wind will stop blowing here in the next week or so and we will be able to make a run offshore and get some real world test results. Once we do this I will post again and give some feedback on performance.
Ok so here is my plug for Powertech and Nettle’s Props (Austin Texas). Nettle’s had the cheapest price I could find and he is on a first name basis with Marcus at Powertech. I had a few questions so JT at nettle’s conference called Marcus and they both spent 30+ minutes talking props and boat performance with me. Never once did Marcus push their prop over a competitor’s he just pushed 4 blades over 3. I highly recommend both companies and if you have any questions about props don’t hesitate calling Powertech they will answer any questions you have.
