Hydromotive first run
- Thread starter xb03
- Start date
Jay Martin
Active Member
Add one pitch for cup is correct, this is a mistake made by one of the industry's best prop guy, (I've seen it happen)..
Last edited:
Jay Martin
Active Member
Oh! One thing I might add is I'm running a Yamaha so I make my HP at lower rpm's than the Merc's.
I have no reason to lie about the numbers, I could have said 90.00 mph but I posted the truth of 89.97...:smile:smile...
I have no reason to lie about the numbers, I could have said 90.00 mph but I posted the truth of 89.97...:smile:smile...
Last edited:
XB03 you have a 6750 limiter correct?
With a 26 pitch at 6850 on mine it puts me in the 86-87mph at very most area. I would look for 85-86 with 100rpms less.
Jay:
So I just want to make sure I understand what you are saying...
You said 6400 rpms, 1.86 gear ratio, and a 28 pitch ran 89.97mph with a Yamaha powerhead. So.... if I would put a Merc powerhead on your EXACT same setup and turned the exact same rpms, the Merc powerhead is going to run slower?
I am also VERY confused how your math is coming out to 5% slip with the numbers you stated. It does not come out to 5%... It comes out to approximately 1/3rd of a percent.
With a 26 pitch at 6850 on mine it puts me in the 86-87mph at very most area. I would look for 85-86 with 100rpms less.
Jay:
So I just want to make sure I understand what you are saying...
You said 6400 rpms, 1.86 gear ratio, and a 28 pitch ran 89.97mph with a Yamaha powerhead. So.... if I would put a Merc powerhead on your EXACT same setup and turned the exact same rpms, the Merc powerhead is going to run slower?
I am also VERY confused how your math is coming out to 5% slip with the numbers you stated. It does not come out to 5%... It comes out to approximately 1/3rd of a percent.
catfish123
Well-Known Member
- Joined
- Mar 15, 2005
- Messages
- 1,938
- Points
- 38
How much cup does it have to be before you start adding an inch of pitch? In all 3 of the OT's that I have run, I never thought any of those OT's had much cup as compared to countless other props I have run. They were all virtually "cupless"...........as was my 1st wife on bra size.........LMAO
catfish123
Well-Known Member
- Joined
- Mar 15, 2005
- Messages
- 1,938
- Points
- 38
Does a motor with more HP in the lower rpm band, and the same gear ratio as another, produce higher speeds at the same rpm's with the same prop? That really makes no sense at all to me but I'm willing to continue learning.
catfish123
Well-Known Member
- Joined
- Mar 15, 2005
- Messages
- 1,938
- Points
- 38
Please understand, I'm absolutely not questioning your achieved speeds. The "effective pitch" of the prop you are running IS either greater than a 26 for whatever reason OR you are turning more rpm's than you think you are. Some brands of props just simply are more steeply pitched than stated/stamped, OR they are being measured by a different standard than the one used by other prop manufacturers. I proclaim myself to be an expert on these things although I have no formal training or practical knowledge of anything I post about............LOL
Maybe the gears were swaped out for 1.62, it's stamped 1.87 tho. But, it is bothering me I need to find out whats up, and the hole time I was thinking I had a fast boat lol. Thats why I need a good day to try the hydromotive because I know it's an untouched 26p.
catfish123
Well-Known Member
- Joined
- Mar 15, 2005
- Messages
- 1,938
- Points
- 38
Maybe you have the boat that ran 101.8 mph with a 225 Promax in the Bass and Walleye boat magazine. :wink:wink:wink Don't let it bother you...........be hoppy!
Jay Martin
Active Member
My HP is only or lets say about 235 at the prop, I can't answer the question about lower rpms and horsepower except it did what it did.
I use the Mercury web site prop slip calculator, Todd and I talked about this when I first got the prop from him, He came up with the same numbers.
Heres the link to merc site, type in my info which is 1.86 gear, 6400 rpm, 29 pitch prop 89.97 mph it will equal 5%
http://www.mercuryracing.com/propellers/propslipcalculator.php
Let me know if you guys come up with something different.
Heres something else to blow your mind, I tested a 28 Turbo TXP O/T 4 worked by me, 1.86 gears, 6100 rpm, 88.2 mph/gps = 2%
I use the Mercury web site prop slip calculator, Todd and I talked about this when I first got the prop from him, He came up with the same numbers.
Heres the link to merc site, type in my info which is 1.86 gear, 6400 rpm, 29 pitch prop 89.97 mph it will equal 5%
http://www.mercuryracing.com/propellers/propslipcalculator.php
Let me know if you guys come up with something different.
Heres something else to blow your mind, I tested a 28 Turbo TXP O/T 4 worked by me, 1.86 gears, 6100 rpm, 88.2 mph/gps = 2%
Last edited:
Jay Martin
Active Member
Todays your luck day, I know a guy that has one for sale with nitrous, the nitrous is for hole shot...It's for sale on this board....
Back to the lower rpm thing, All I can tell you is my yamaha makes its HP down low vs. The Merc power band which in your case what? 6700 or so, the yamaha has more torque at lower rpm to be able to turn more pitch at that rpm.
It's all in the port timming from what I'm told. I try not to understand it to much, I just focus on making the props work with it....:wink....
Jay Martin
Active Member
Actually the cup thats calculated in is the trailing edge, not the tip cup.
catfish123
Well-Known Member
- Joined
- Mar 15, 2005
- Messages
- 1,938
- Points
- 38
Jay, you had said this in an earlier post so I thought you meant that since you make your HP at lower rpm's than the Merc's that somehow that was an explanation from you concerning why you achieve higher speeds than a Merc at 6400 rpm's.