I would like to try a Yamaha 27t1 prop. I will pay shipping both ways and provide a deposit. I fish Lake Lanier which is a deep lake with few obstructions to hit. I currently run a 25t1 with cup added on my '14 Z520C with SHO 250 recently flashed to 300. Curious to see what a bigger prop will do for me and seems borrowing one is my best option before buying one if it doesn't help.
Thank you, John
Hey John, I can't help you with a prop, wish I could but I have a 2010 250 SHO with around 300 hours on it since new. It like all of the very early motors has had the powerhead replaced by Yamaha so about 100 hours of the 300 total are on the replaced powerhead. I've often thought about getting my engine flashed to 300. My 2010 FX21 is actually rated for 300 so I wouldn't have any insurance liability issues. If you don't mind sharing who did your flash and did you have them raise the rev limiter or did you leave it the same as original spec. If I get mine flashed my goal would be a higher mid range cruise speed by running a higher pitch prop. I have the original 25T1 SHO prop and it is perfect but I would think I could go to a 27T1 or T2 if I do the flash. For reliabilty sake I don't plan to have the rpm rev limit raised. If you have had a chance to run your boat after the flash is the extra power very noticable? If you had it to do over again would you still get it flashed to 300? One last question which you may not know but your opinion is valued. If you go to the 27P prop do you think you will still have a very good holeshot? Will the extra power allow the engine to drive the higher pitch prop fast enough to not have the boat be sluggish coming out of the hole. I ask that because perhaps one of the reasons for having the rev limit increased on the flashed engines is so the same pitch prop as pre-flash can be run and not hurt the holeshot, it that makes sense. I'm sorry for all the questions - the engineer in me thinks way too much about all the angles. Thanks in advance for your help.
I had the limiter raised to 6500 rpm but can't get above 6100 after flash. Hydrotec did the flash and it cost about $600 plus shipping. I see very little increase in top end speed but I do notice the mid-range power quite a bit. The existing holeshot is VERY good so I don't think the increased pitch will ruin it. But, that and topend are the reason I am trying to borrow a prop instead of buying one and being disappointed.
Would I flash it again knowing what I know now after probably 8 months of use, no! I really notice minimal improvement overall.
John
Take the cowling off and run it WOT with no cowling. I've seen a few SHO's pick up 400-500 RPMS in lakes with elevation.Originally Posted by John Hagins
Same result for most with a 250 HO after a flash. The 250 HO already makes more at the prop than 250, so the gain is minimal. The 300 flash is just a factory 300 map and that is what everyone is getting. You can stretch them out over a mile or so and they will build a little more RPM's, but not much unless you go with a shorter pitch prop. All of the dyno charts show they make almost max HP at 5500 after the flash, but somehow they pick up another 20 or so flywheel horsepower once you get past the "Dead zone" in the power band and get some build on it, but it takes a long distance. Flashing a 200 HO is well worth it, 250? Not so much IMO, but you do gain some torque in the mid and low end.
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John and Hammerhead, thank you so much for your real world experience. Your input probably saved me $600. I agree the 250 SHO is a strong motor, that is why our 250s run a 25P prop and the guys who repower their 250 2 stroke Merc ProXs motors to the 4 stroke have to drop in pitch to 23 or in some cases drop even further. I'm not casting any rocks here at Merc but Horsepower should be horsepower and it never made sense to me that a 250 4 stroke with much larger displacement (4.6 L vs the 2 stroke 3.0) would have to drop in pitch so much. Maybe it has something to do with emmisions, I don't know but I love my SHO. I do wish we didn't have the posts every so often about one blowing up. I think all bass boat engines should be more reliable but it doesn't seem to be happening.
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