Talk about it all the time!!!!!!!! http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/boardstuff2/beers.gif
Printable View
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spider1 »</TD></TR><TR><TD CLASS="quote">Lou it also depends on what you are looking for and what motor you have.
Like mine has a limiter of only 6150 so a small prop will not give me the speed and with the 1.75 I have to run such a large prop to stay out of the limiter that there is very little difference between the two gears.</TD></TR></TABLE>
That was my point in having a poor holeshot but quickly getting back around them because they cannot reach the numbers up top. I have been waiting 3 weeks for a smaller pitch prop and as soon as I can send the 30 back I will!
My motor is like yours Connor, my limiter is roughly the same so the gears I believe are a wash due to running a bigger prop for the top end.
I am not going to comment of the diet as I believe I am either the pot or the kettle! http://www.bassboatcentral.com/smileys/Laugh.gif
Lou, I dont see how your going to be able to keep a 26 off the limiter. Its gunna have to be very stiff.
All of ya can KMA on the diet chit! I've been on a damn diet for a month and Lou's lost 15 #'s........I've lost 5 http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif
Just get in the damn boats and go fishing! http://www.bassboatcentral.com/smileys/thumbsup2.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/boardstuff2/beers.gif
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PetiteBass »</TD></TR><TR><TD CLASS="quote">All of ya can KMA on the diet chit! I've been on a damn diet for a month and Lou's lost 15 #'s........I've lost 5 http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif
Just get in the damn boats and go fishing! http://www.bassboatcentral.com/smileys/thumbsup2.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/boardstuff2/beers.gif </TD></TR></TABLE>
My My a little touchy ain't we! http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spider1 »</TD></TR><TR><TD CLASS="quote">
My My a little touchy ain't we! http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif </TD></TR></TABLE>
http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/newyear1.gif
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PetiteBass »</TD></TR><TR><TD CLASS="quote">All of ya can KMA on the diet chit! I've been on a damn diet for a month and Lou's lost 15 #'s........I've lost 5 http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif
Just get in the damn boats and go fishing! http://www.bassboatcentral.com/smileys/thumbsup2.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/boardstuff2/beers.gif </TD></TR></TABLE>
PRICELESS........................... http://www.bassboatcentral.com/smileys/Laugh.gif
I'm in a little diff situation than most but I went for the 1.75 gears for the low and mid range acceleration. That being said there is nobody out here to swap props with because my smallest i run is a worked 28p Bravo and Hydro q4x ob and the largest on the other boats in my area is a 26 trophy and 26 Hydro q4x ob. I do have a 26TRO4 that is probably close to a 27 1/2" with all the work thats been done to it and I'm all over the limiter if pushed.
Lou, good luck with your testing. It seems that the gears make up for about 2" in pitch.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Hydrilla »</TD></TR><TR><TD CLASS="quote">Lou, I dont see how your going to be able to keep a 26 off the limiter. Its gunna have to be very stiff.</TD></TR></TABLE>
Rich, Probably be at, or on the limiter but that is no different then with the 28 and 1.75 gears..
Thanks Dean,,, if nothing else this is a great learning experience..
Now you may say that just go up to a 30 with the 1.75.. well if the hole shot is a touch better then a 28 and 1.62 gears as is excelleration and the top #er is the same between them then naturally you would lean toward the 1.75's and the 30 pitch.. http://www.bassboatcentral.com/smileys/ohwell.gif http://www.bassboatcentral.com/smileys/doh.gif
Hell with this, LETS RACE!!!!!!!!!! http://www.bassboatcentral.com/smileys/devil.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/boardstuff2/beers.gif
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PetiteBass »</TD></TR><TR><TD CLASS="quote">All of ya can KMA on the diet chit! I've been on a damn diet for a month and Lou's lost 15 #'s........I've lost 5 http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif http://www.bassboatcentral.com/smileys/mad.gif
Just get in the damn boats and go fishing! http://www.bassboatcentral.com/smileys/thumbsup2.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/boardstuff2/beers.gif </TD></TR></TABLE>
Now I know why I got punched when I came home!!!!!! http://www.bassboatcentral.com/smileys/eek.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/roll.gif
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Largemouthlou »</TD></TR><TR><TD CLASS="quote">
Now I know why I got punched when I came home!!!!!! http://www.bassboatcentral.com/smileys/eek.gif http://www.bassboatcentral.com/smileys/Laugh.gif http://www.bassboatcentral.com/smileys/roll.gif </TD></TR></TABLE>
Now that is what I like!! Us getting you in trouble!! http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif http://www.bassboatcentral.com/smileys/roll.gif
There is one other thing for the 1.62's and that is the smaller prop should be more efficient so it should deliver more speed then a larger prop with the 1.75.
So a 26 and 1.62's should run faster say at 6400 rpms then a 28 and 1.75 at 6800 rpms. But how much faster are we talking 0.1 or would it be 1.0 mph that is the question!! and if it is the same speed then with the 1.62 and 26 you are working your motor less and you still have 600 rpms to the limiter vs on 200 rpms.
Go borrow a big prop from Brent 34-36P and go run a realllly big number with the 1.75's. http://www.bassboatcentral.com/smileys/devil.gif
John: Some really great technical info you are providing here as well as everyone else http://www.bassboatcentral.com/smileys/thumbsup2.gif I never thought about the prop RPM's being the inverse of the gear ratio but I'm not sure if theoretically you want to more or less prop RPM's maybe someone can chime in on that.
John I have a couple of questions, I thought 29" of pitch was the optimum pitch for a prop to be but is that dependent on gear ratio or is that a static number?
How does the rake effect the efficiency of the prop as well ? we all think of pitch and we are doing a lot of testing on diameter but is there an optimal rake angle for a prop as well?
John I was told that 14.5" Merc racing had determined to be the optimum diameter for a prop yet we are now running props of up to 15.5" in diameter is there a ratio of pitch to diameter that is optimal? You can elevate a bigger diameter prop more than a smaller one generally but a bigger diameter will turn less RPM's than a smaller one so with big diameter you can get by with less pitch and with a smaller diameter you need more pitch. See what I'm asking?
Lastly Lou, Merc says the 300X is WOT at 6200 to 6800 right?? but on your engine do you have an accurate idea of where the HP to Torque curve is? and what the peak HP is at what RPM? One last thing your 300X is fully stock right?
This is a very interesting thread I hope some of these questions I ask are not hijacking it but I feel they are all relative to the goals we are looking for here http://www.bassboatcentral.com/smileys/thumbsup2.gif
Eli I think there is a lot more to just the prop size, diameter, rake angle and blade design as to the efficiency of the prop.
It has a lot to do with hull, motor limiter, weight and weight placement.
For example take Lou's rig and my rig. We both have about the same in HP but he has a limiter of 6800 and I have one of 6150. That alone will play a huge role in prop selection if the gears are the same. If you prop both boats to say right at but off the limiter he Lou should have a much better hole shot with 1.62 even if I would go to the 1.75 gears.
Oh and the bigger the numbers in gear ratio the slower the prop will turn at a given rpm.
A gear ratio of 1 to 1 at 6000 motor rpms the prop turns 6000 rpms also
After that the prop speeds starts to drop.
6000 rpms and 1.62 gears the prop is turning 3703
6000 rpms and 1.75 gears the prop is turning 3428
It still is best to bolt on a prop run it and see what she will do for ya!!
http://www.bassboatcentral.com/smileys/roll.gif
First off there are alot of veriables in every direction. I think that comparing the gear ratios it shouldn't matter about the prop specs. My opinion is that for everyhting to be equal the motor has to be proped at the same rpm which should be at peak HP and TQ (6300 or so, just my .02). As far as optimal pitch has to do with the angle of attack that the blade meets the water. Too little or to much you do a burn out. If you straiten the blades you have no area to push the water forward. Rake does change things but you must also remember as you twist the blades up in rake angle you loose diameter, as you loose diameter you increase rpms. As far as optimal diameter that merc claims is for the average of all boats. Champ boats run real real small diameters, we seem to find that larger diameters help us. I think that is because we jack them up so sky high. I noticed that on a buddys heavy ranger that a smaller diameter laser ran better than a bigger diameter tempest due to the fact that the lu is burried....And again less diameter means more rpm and slip to get it going.
I would like to heart more of exactly what handling characteristics are different. The only thing that I can think is that the smaller gears are helping with hole shot and that the trim jacking sequence should start a little earlier than with the 1.62's. It's probably breaking loose easier. On a race car smaller gears with the same size tires makes it easier to do a burn out............................................... .......
What do you all think? http://www.bassboatcentral.com/smileys/stirthepot.gif http://www.bassboatcentral.com/smileys/popcorn.gif
Spider: I fully agree there is FAR more to it than just rake, diameter, pitch, blade design and even hub issues to add another variable http://www.bassboatcentral.com/smileys/thumbsup2.gif Yeah I know here we go agreeing again and that doesn't happen often http://www.bassboatcentral.com/smileys/wink.gif http://www.bassboatcentral.com/smileys/smile.gif But for this discussion were all talking about those variables in relation to a Stroker I assume?
I agree also that while Lou's rig and yours weigh about the same the characteristics of each of your motors is very different based on many differences not just the limiter difference. While I haven't seen a print out on either of your dyno charts while both have about the same HP I'm sure their curves as well as torque curves are different.
What I'd like to know though is how some of my questions might work out in regards to John's extensive knowledge of mechanics and function. If you have a prop with more diameter you can surface it more but it's harder to turn pitch for pitch so at 14.5" of diameter for example you could turn a 32" pitch prop a lot more RPM's than a 32" pitch prop that had a 15.5" diameter, but which is more efficient? Is there a theoreticaly optimal number for pitch, diameter, and rake angle?
I also would like to know about your last paragraph where the gear ratio goes up the prop RPM's go down, yes I understand it but is there an optimal ratio there or does it matter?
Lastly of course it's best to bolt on anything you can get your hands on, Kurt taught me that http://www.bassboatcentral.com/smileys/wink.gif a long time a go but is there a method here of helping narrow your search?
Eli, theroticals get you in the ballpark. There are way too many variables, as others have mentioned, to set an absolute best anything. To start with, a 25" pitch prop is only 25" at one distance from centerline, the pitch varies with an average pitch of 25". The blade shape, including area of blade with respect of distance from the centerline, alto determine the major thrust area, where effective pitch is most accurate.
Trailing edge cupping adds pitch and stern lift. Tip cupping adds bow lift, as does rake.
Yon can write a 500 page technical article and still not cover all the variables. All we can do is experiment and see what works best on our setups, and let the theories just be a guideline, not an absolute.
John: Yes "ball park" but in theory is there a certain optimal ratio?
For example my question about a 14.5" diameter prop VS a 15.5" diameter prop each having the same pitch lets say 32" or 34" The 15.5" can be elevated more than the 14.5" but does this theoretically make up for the added drag of the extra 1" diameter? I assume you could use a prop that is less pitch if the diameter was greater and get the same RPM's thus more efficient ??
Lou: From what you have told me by phone I can't figure your situation out either except for Jason's boat has a different set up and weight than yours but just changing the gear ratio shouldn't give you the driving issues you are having and you can flat out drive with the best of them so it's not in your head or in your ability at the wheel http://www.bassboatcentral.com/smileys/wink.gif
The larger the diameter of the effective pitch area, the larger the pitch should be for maximim efficiency. But the prop diameter is not always proportional to the diameter of the effective pitch area. Props with blades that have a lot of area near the OD will typically be more efficient with a higher pitch than props of the same diameter and pitch but with less blade area at the OD.
Visualize a high 5 blade vs an uncut performer blade.
Surfacing just adds another variable, where you need more blade area near the OD. OD= outside diameter.