Do You Understand Boat Prop Size, Pitch and Diameter?
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- Опубликовано: 5 сен 2024
- This video is a great quick explanation of boat props to hopefully help you on your next prop purchase for your fishing boat. Ray Brazier is considered an authority on rigging boats with 4 decades of experience and helps T-H Marine develop boat products to make life easier on other anglers and boaters.
Fantastic video thank you! Best explanation and short n sweet - bravo good sir. Been on the fence between going up to 15.3x19 or sticking with my 14.5x19.
Clear as mud...
One more factor to consider though. IF your gear linkage is not set up right, you may (as in my rig) have the accelerator all the way down and still room to go, so you are not at WOT. Adjust--or have it adjusted before anything else, make sure you have full stroke.
Thanks for taking the time to your share your video and knowledge with us.
It is really appreciated!
I have a 5 mtr. RIB with (x2) 40 hp Enduro outboard motors
(5500- 6000 rpm. max.), both have three blade props 11 3/8 x 12.
The Boats max load capacity is 1 ton and although I am no
way any where near that at all, it seems slightly heavy at the
transom, once she is loaded up with dive gear, since it is very sluggish,
to get up on the plane.
I am looking to increase the power, for towing applications, as
we are doing small salvage operations.
From what you were saying, it seems that a 4 Blade prop is the
way to go and a 12, or 12 1/4", or 12 3/8" by 13 pitch seems like the way to go,
with out it effecting my top end RPM to much, or putting to much strain on my
motors.
From the research that I have done, adding an extra blade looses about 500 - 800 rpm!
Adding pitch looses about 500rpm per 1 pitch, as does increasing the diameter per 1/2 inch.
I am having trouble finding a 4 Blade 11 3/8" by 13, 14 or 15 pitch propeller.
Many of the suppliers offer a smaller or larger diameter propeller.
I guess my biggest concern is over load and stalling the motors out of the gate!
Increasing Diameter moves more water, but increases the surface tension, as does
adding a fourth Blade!
Increasing the pitch on the standard 11 3/8 size prop I have will work to a point, at which
point the cavitation will start to reduce any benefit you might have gained and in fact start
to cause damage too the prop, bearings and or engine!
I am a logical minded person and to a large extent, a self taught engineer.
My limited knowledge and research, suggests that I increase the Diameter, to cancel out
any possible cavitation, perhaps the next size up, perhaps a 12 inch prop, which should
allow for a significant increase in pitch, say maybe a 15, or 16, but will increase the engine
stalling factor, especially with the extra blade, which gives a quicker out of the hole response
an onto an even keel!
I was toying with the idea of putting a 4 Blade 12" by 13 or 14 pitch on.
My motors idle at 800-1000rpm!
Increase the idle speed?
Do you have any suggestions?
Thanks!
BIG HELP GUYS... you guys make life so much easier. thx again
That is the exact information I was looking for. Thank you sir
Glad it was helpful!
Thanks points me in right direction. My 4.3 V6 will over rev.
I also have a 4.3 v6 what size do you have if I may asks theying to learn to get better more speed
@@fishkingize book says 4800 max rpm. Its going 5500 if i let it.just went looked took pics of what marina gave me. Its close.19 ran it 3 times this summer.49 mph.20ft cuddy. 4.3 v6. Took pic of numbers on prop.gess watch this video again
Ok i just a new prop I went from 4 blade to a 3 blade look for more speed I let you know how it go
a bigger prop can cause the boat to go slower, the engine may not be able to reach the optimum range in its power curve, one must realise that the prop has to be matched to the power curve. A large diameter prop to go faster will need less pitch than a smaller dia prop to allow it to reach a rpm that matches the engines power curve.
Yep exactly, me and my buddy got the same boat, 25hp 2 strokes, I run a 9.9x11 he runs 10.5x11 and my boat is faster by a good 6 mph on GPS.
3 is faster than 4. And 2 is faster than 3. So 1 blade must be the best
GEARING ie MATCHING LOAD TO SPEED
Cool
why do some props have a sort of scoop at the tip where the exhaust gas comes out & others like your one is straight
I have a 24foot checkmate closed bow 454 7.4 big block the moter has had minor upgrades alpha 1 outdrive i have 23 pit h prop but not much speed would a 25 e to much
Question !!
Can a
Mercury Marine Alpha 4 Blade Aluminum Propeller 16pitch work on Yamaha Engine ???? if yes what hp engine required ????
Good video
Your wrong a larger diameter prop will give you more of a hole shot and lower top end cause it’s like a fan blade every inch of dia is worth 2in of pitch
thanks
When I go full throttle trying to get out the hole my prop starts to slip bad what will fix this? Thanks
Sounds like a bad prop hub. Mine did the same thing
Thank you sir
Our pleasure Shawn.
How do you figure out the tongue weight of the trailer
Hi JJ. It's usually located on placard on the trailer tongue. Also, if you know your trailer weight, your tongue weight will usually be 10-15% of your gross trailer weight.
...Engine RPM at Tachometer Redline....
LOL Hey diddle diddle, right down the middle! LOL
Do you understand, that you dont understand, that people dont have to understand haha.
You talked about pitch then Diameter so a 10 X 12 prop would have 10" pitch and 12" diameter ?
Or is it the other way around?
10 would be the diameter and 12 would be the pitch the first number is always diameter.
Another one that everyone nows about
Which number is which??? is diameter the first or last number???
First
He really doesn't answer the question: for a given boat, how do I know WHICH pitch to chose? Yeah, he says the one that will give you the most speed at the maximum RPM. Ok, fine, so my Yamaha's peak RPM--I am told, is 6000, so I want the size and pitch to give me the most speed AT that RPM. Fine, so start again, WHICH of the sizes and pitches will give me that? Go buy em all, and try em one at a time until I know. Give me a break.
GPS your rig, if on the top end your giving it more throttle (adding more rpm) and the boat is not gaining speed you need more prop (pitch)
See, I get that Snake--I get how you discover AFTER buying a prop that it is the right or wrong prop. Check. I'm talking about how to ESTIMATE the proper prop to purchase, not how to evaluated it AFTER the purchase and installation. But I think I got it sorted, at least a ballpark estimate and just received my new prop. I'll try it out shortly and see if I hit it close enough to keep. What I find from most, is exactly what I ran into when I was young and working on cars, you know 'just bring it back if it doesn't fit", same deal here--just run the test and if it is the wrong pop, buy another. For sure, we can do better than that.
Pitch dimension times rpm will get you distance over time, you can extrapolate that to mph and then throw your slip factor in to true it up. Top speed for your hull has to be a reasonable expectation based on weight, design and horsepower. How fast do you want to go and how hard do you want to come out of the hole, that's the question. If you have a light fast hull with lots of power on tap, you will have a small slip factor and you will get good response with any prop change. I have 3 props for my malibu skier, makes the boat way more versatile.
@@jimquantic find a great prop shop they help u by selling you a prop but they loan them out 1 at a time until your happy with it...also they know Thier business and get u close from the start...like the other guy a couple different props are fun to have. One for top end speed and a nice power prop for tubes and wakeboarding etc....
thanks, but just know that not only "guys" are interested in learning about props!
Understood, but a better generic term could be used such as "all" or "folks". I have been trying to use these in my conversation as well. Quick search on internet came up with this short article that kind of sums up the issue for everyone: www.alternet.org/story/48527/can_the_term_%22guys%22_refer_to_women_and_girls
SMH who let the liberal hippy in yall?
S. Scherer liberal cry baby