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Posts: 284
Location: Eagan, MN | Hi Guys
Gotta a question... I recently re-powered my '03' 621 with a 250 Yamaha SHO. I kept the prop from my old motor; a 21P Rev 4. The motor is mounted in the highest hole. I've lost some hole shot with this new set-up, but gained some top end, running about 55 mph at WOT with one guy and half a tank of fuel. .
I'm not totally unhappy with the performance, but the motor is turning at only 5200 RPMs at WOT, when 6000 RPMs is the desired threshold. Can't help but feel I'm leaving better performance on the table with the prop I'm currently running.
I want to get the most performance out of this motor. Anyone have insight they want to share? Best resource for props in or around the Twin Cities to help me get the maximum performance?
Thx!
Brian
Edited by BrianF. 10/9/2017 4:34 PM
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Posts: 483
| from your result a minimum of i pitch lower would help even 2, the rpm would get up to 6000 + much better holeshot but i am no expert. on my new to me boat last year a 4 blade 25 to 21 gave it great hole shot and 800 rpm at wot |
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Posts: 457
Location: Minneconia | Try a 19p rev 4 or maybe a 21/22p Bravo 1 FS. could try a 20 or 21p Bravo LT but not sure it would be a good fit with that hull design.
I would call Ricky @ Brainerd Props for help, he's about as good as it gets in the midwest for propping Rangers.
Edited by Dirt Esox 10/9/2017 5:59 PM
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Posts: 3480
Location: Elk River, Minnesota | Hiya!!
Just want to make sure I understand the set-up correctly... The motor in the highest hole. If I understand correctly the motor is mounted about 3" off the lowest point of the transom?
If so, then I would agree that a pitch change is likely in order. In your case, you have a boat that is heavy, and with a 250 on it, I believe you are maxed on HP. A general guideline for pitch change is for every inch in pitch change, you can expect a change of 150 to 200 rpms (down in pitch -> up in RPM and vice versa) There is a limiting factor to this as well as getting too much pitch, the motor just does not have enough in it to turn it. For example, on my rig, I can run an 18 pitch prop and reach my max of 5500 RPM, but if I go to a 20 pitch, I can't reach 4600 RPM... The motor just does not have enough in it.
Also, I'm wondering if your new motor has the same gear ratio as your older motor. If they are different, that would explain a bit as to why you are not seeing somewhat the same performance out of the motor...
In your specific case, if you have a 19 pitch Rev4 (as suggested above), I feel that would be a good call as well. It should increase your RPMs by around 400 or so, but you may see more than that. Now...if it gives you those 400 rpms and your motor is mounted in the lowest position, moving the motor up a couple of holes will give you about 200 more rpm. This is a tricky call though as I believe you may have a setback on your boat so you might lose too much handling if you get too high. My gut says you'll be alright. The only way to know is to try it and see what happens. In many cases, you can be at higher motor heights...just because you have the 4th fin in the water with the prop, increasing handling significantly because you have more surface area contacting water with thrust.
I'm betting the 19 pitch will be really close.
Steve |
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Posts: 284
Location: Eagan, MN | Thx for the help gentlemen. I'm going to try both a 19P and 17P prop. Doing the simple math, one of these should get me in the preferred 6000 rpm range. The hole shot should improve, but I'm hoping the top end performance and handling will not be compromised. I'll report back on the results, but in the meantime remain open to other suggestions. |
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Posts: 457
Location: Minneconia | If you want improved top end AND hole shot I'd try the Bravo. Rev 4 you will lose top end as you drop pitch but gain rpms and fantastic hole shot, guaranteed. Rev 4 has better "grip", Bravo is a little "loose" but I think you'll be happier with a Bravo 1 FS(not LT)on that hull.
I wouldn't even bother with the 17p.
Edited by Dirt Esox 10/13/2017 9:39 AM
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Location: 31 | Dirt Esox - 10/13/2017 9:36 AM
If you want improved top end AND hole shot I'd try the Bravo. Rev 4 you will lose top end as you drop pitch but gain rpms and fantastic hole shot, guaranteed. Rev 4 has better "grip", Bravo is a little "loose" but I think you'll be happier with a Bravo 1 FS(not LT)on that hull.
I wouldn't even bother with the 17p.
x2 the 19 gets me to 6000 with a top speed of 49 on an 08 621 with a 250 off shore. |
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Posts: 284
Location: Eagan, MN | Update: I put a 19P Rev 4 on the weekend to test. The hole shot improved considerably and the mid-range acceleration was better as well. Depending on wind direction, I got 5700/5800 rpms at WOT and 53/54 mph with a tournament load and one guy. Probably lost 1 mph at WOT vs the 21p. Overall, this was an improvement in performance. The only downside - and this could be a misperception on my part - is that I don’t feel that the 19p carries the bow as well as the 21p. I’m not sure why that would be the case or if that is indeed true, but that was how it felt. I really wished I had the Bravo FS prop to test but wasn’t able to locate one prior to my testing. Anyway, I think I’ll call it good enough for now. Thanks to those who commented. Your reply’s were definitely helpful. Brian |
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Posts: 457
Location: Minneconia | Sounds like you're headed in the right direction....don't short change your rig, make sure you at least try the Bravo if not this season then next to verify. I have a hunch it will be fantastic with that motor and hull combo, and worth the trouble. Glad you're making progress!
Edited by Dirt Esox 10/24/2017 9:01 PM
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Posts: 284
Location: Eagan, MN | Dirt, both you and Ricky at Brainerd Props recommended the Bravo. I really want to test one, but nobody seems to have one to test locally. Getting them on the Internet is expensive if you want to return them after testing. Shipping and restocking fees add up. It's definitely on my mind though and I probably won't be able to let it go until I try one out. |
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