As the title says, this is a comparison of two four-blade SS props.The first one is a Michigan Wheel Apollo XHS 4-blade SS 14.625x16 prop (otherwise known as the "RidgeKid's Prop"). This prop will be referred to as SS 2010 in the rest of this discussion. The second one is a Solas Rubex HR4 4-blase SS 14.5x15 prop. This will be referred to as SS 2012. Both props are compatible with the Mercury Flo-Torq II hub, and they have been tested with that hub.The test boat is a 2006 245 Cruiser with 5.0 lt 220 hp carb engine and Alpha One Gen II Drive. The SS 2010 test was performed during the second week of May 2010 and the SS 2012, during the second week of May 2012, both on Lake Erie (571 ft elevation). In both cases, fuel tank was full, water and waste tanks were empty, one adult and full complement of season's running gear were onboard, bimini top was folded, and seas were calm. Speeds were measured by Lowrance HDS-5 GPS, fuel flow by Lowrance EP-60R sensor and rpms by the onboard tacho, previously verified to be highly accurate.First, plots of SS 2010 and SS 2012 results:
[img]/media/kunena/attachments/vb/699624=29247-image004.jpg[/img]
[img]/media/kunena/attachments/vb/699624=29248-image009.jpg[/img]Now, a note of caution about the SS 2012 fuel flow results: Just before the SS 2012 run, while setting the tank level, I managed to mess up the calibration of the fuel flow meter. Therefore, the absolute values of the GPH and MPG on SS 2012 plot are not correct. However, the relative values of these numbers are fine, and the shapes of the curves they represent are valid.Next three plots compare SS 2010 with SS 2012:
[img]/media/kunena/attachments/vb/699624=29249-image013.jpg[/img]
[img]/media/kunena/attachments/vb/699624=29250-image014.jpg[/img]
[img]/media/kunena/attachments/vb/699624=29251-image010.jpg[/img]MHP by RPM comparison is quite surprising. Everything else being the same, I would have expected the SS 2012 curve to be shifted more to the right, specifically by 16/15 of the RPM. As they are now, it is as if the two props have almost the same pitch. This must have something to do with the design of the props.SS 2012 gave me a slightly higher WOT RPM. In fact, this was the reason I tried the 15-pitch Solas in the first place. The 16-pitch MW was getting me usually no more than 4550 at WOT, and this number dropped to less than 4400 as the season progressed with no bottom cleaning. The Solas gave me close to 4800 at the beginning of the season (although that number dropped fast as well with bottom build-up).Top speed of SS 2012 was 38.8 mph, compared to 37 mph for SS 2010. I suppose this is partially due to the slightly higher horsepower generated by the engine at the higher rpm. I must add that I was able to exceed 37 mph several times with the SS 2010 prop during various others runs, the best being more than 39 mph. So, I don't know if the top end comparison from just these two runs means much.Looking at the GPH and MPG graphs, we see that both SS 2010 and SS 2012 exhibit very similar behavior. As I said before, SS 2012 fuel flow measurements are skewed, so the only comparisons to be made between SS 2010 and SS 2012 have to do with the shapes of the curves, not the absolute values.Now, some qualitative observations. SS 2012 has phenomenal hole shot. However, SS 2010 is very strong in that regard as well. While SS 2012 should be theoretically better, it is very difficult to discern any difference between the two without doing acceleration plots. One area where SS 2012 is significantly better is in turning. During hard turns, even at WOT, the prop did not cavitate. I did not have to trim in the drive, either. The boat came out of turns with very little drop in speed.Yesterday, I switched back to SS 2010 after using SS 2012 for more than a month. With calibration of the fuel flow meter back to normal, I can see that SS 2010 gives me about 3 to 5% better fuel economy. Since I am planning to clean the bottom regularly, the top end difference is not a big issue. It looks like I will keep SS 2010.CE
[img]/media/kunena/attachments/vb/699624=29247-image004.jpg[/img]
[img]/media/kunena/attachments/vb/699624=29248-image009.jpg[/img]Now, a note of caution about the SS 2012 fuel flow results: Just before the SS 2012 run, while setting the tank level, I managed to mess up the calibration of the fuel flow meter. Therefore, the absolute values of the GPH and MPG on SS 2012 plot are not correct. However, the relative values of these numbers are fine, and the shapes of the curves they represent are valid.Next three plots compare SS 2010 with SS 2012:
[img]/media/kunena/attachments/vb/699624=29249-image013.jpg[/img]
[img]/media/kunena/attachments/vb/699624=29250-image014.jpg[/img]
[img]/media/kunena/attachments/vb/699624=29251-image010.jpg[/img]MHP by RPM comparison is quite surprising. Everything else being the same, I would have expected the SS 2012 curve to be shifted more to the right, specifically by 16/15 of the RPM. As they are now, it is as if the two props have almost the same pitch. This must have something to do with the design of the props.SS 2012 gave me a slightly higher WOT RPM. In fact, this was the reason I tried the 15-pitch Solas in the first place. The 16-pitch MW was getting me usually no more than 4550 at WOT, and this number dropped to less than 4400 as the season progressed with no bottom cleaning. The Solas gave me close to 4800 at the beginning of the season (although that number dropped fast as well with bottom build-up).Top speed of SS 2012 was 38.8 mph, compared to 37 mph for SS 2010. I suppose this is partially due to the slightly higher horsepower generated by the engine at the higher rpm. I must add that I was able to exceed 37 mph several times with the SS 2010 prop during various others runs, the best being more than 39 mph. So, I don't know if the top end comparison from just these two runs means much.Looking at the GPH and MPG graphs, we see that both SS 2010 and SS 2012 exhibit very similar behavior. As I said before, SS 2012 fuel flow measurements are skewed, so the only comparisons to be made between SS 2010 and SS 2012 have to do with the shapes of the curves, not the absolute values.Now, some qualitative observations. SS 2012 has phenomenal hole shot. However, SS 2010 is very strong in that regard as well. While SS 2012 should be theoretically better, it is very difficult to discern any difference between the two without doing acceleration plots. One area where SS 2012 is significantly better is in turning. During hard turns, even at WOT, the prop did not cavitate. I did not have to trim in the drive, either. The boat came out of turns with very little drop in speed.Yesterday, I switched back to SS 2010 after using SS 2012 for more than a month. With calibration of the fuel flow meter back to normal, I can see that SS 2010 gives me about 3 to 5% better fuel economy. Since I am planning to clean the bottom regularly, the top end difference is not a big issue. It looks like I will keep SS 2010.CE
Comment