I went from the 2-stroke 250 pro xs to 4-stroke 250 pro xs on a 920. When changed to 4 the prop changed from 25 to 24 pitch fury. There is not .5 mph difference top end on either end. It seems like the 4 maintains speed with big weight loads better and has more torque. I also think fuel consumption is pretty close on the two.
Went from a 921 Pro XP with 2 stroke to 921 Elite with 4 stroke and top speed is the same. Very happy with the change to 4 stroke, lots of advantages over the 2S, and top speed is the same.
I had the SHO on the 721 and have the 4XS on the 921... IMHO, the 4XS is stronger, particularly at hole shot (maybe the 4.6L v 4.2L???) than the SHO.Originally Posted by XChris1632X
BigBrown, it's a 24 pitch 4 blade.
Thanks Coach!
That's interesting. I've owned 4 SHO's and when comparing them to HPDI and OX66 Yamaha engines on the same rigs, I was able with the SHO to go up in pitch and maintain the same holeshot with better top end. On the other hand it seems the Merc 4s guys are having to go down in pitch but say it has more torque???? That doesn't add up to me.
This is my struggle. The result of RPM vs Pitch vs speed seems to be very cloudy to me.
-2016 Phoenix 721 250 Pro XS
-Old Rig-2006 Triton TR-196 200HP Optimax
The only thing I can figure is this....I owned my 4 SHOs during Yamaha's first 3 years of production. So were those motors pushing the top end of the 10% rule and now the new Mercs and SHOs are on the bottom end of the 10% rule? For those that don't know or understand the 10% rule, all outboards can + or - 10% of its stated HP, so that can be a swing of 50hp on a 250hp outboard.
Everyone says the TM2 gearcase on the mercs has been massaged on the 4 strokes and supposedly props are more efficient. That's why the props have to be smaller. Still seems odd. I turn a 24 Fury 5650 rpms on my Triton and that will get me to 75mph.
The numbers don’t add up. That’s -2 % slip???
Those numbers don’t add up. That comes up with a -2% prop slip? Are you sure you rpms are only 5650 wot?
You have to remember the fury props are very stiff. 24 fury is same as a 25 tempest. It is possible my tachometer could be a little off too.
I can tell you guys that the prop slip numbers don't add up on either of my Fury Props, the 3 blade or 4 blade. They both run with almost no slip according to the prop calculator using smartcraft RPM 3's and GPS speeds. I know for sure how fast I'm going and how many RPM's I'm turning but the slip or pitch can't be right. I gave up worrying about that, I'm happy with my holeshot, mid-range and top end with either prop but just for knowing's sake it would be nice to figure out. Just more info they both run best pretty high.
R brand boat but the Mercury prop slip calculator shows the same thing for my boat. 73.5 at 6100 RPM with a 1.75:1 gear ratio and 23P Fury 3 blade.......3% prop slip is what the calculator says. Like you. I'm very happy with the performance but can't explain why the calc's show my prop slip so low. Speed recorded on my Carbon 12 and RPM on my smartcraft.
2019 Ranger Z520C DC / 250 Pro XS 4 Stroke
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