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Which prop would you recommend?

9/14/19 @ 9:40 AM
ORIGNAL POST
fuzzyfishin
User since 3/26/07

I have a 2000 1850 crestliner sport fish. I’m getting 42 mph gps. at 4209 rpm. The prop I have is a solas 14/21.  Think about going to 14.25/19. Looking for best fuel economy.

Motor is 175johnson 2 stroke wot 5250-5750

Looking for alum and stainless.

What are your thoughts. 

Recently bought this boatThanks

DISPLAYING 11 TO 19 OF 19 POSTS
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9/15/19 @ 5:15 PM
fuzzyfishin
User since 3/26/07

Ranger, I thank you for all the info.

I do fish Michigan when I can and love it. Just haven’t been able to get out this year. I’m setting this boat up for salmon as I did my last boat.

I think I will start with 19 pitch. I was running with a loaded boat (kicker and gear as well as my wife) don’t think I will hurt anything with a 19. Then go from there.

My last boat was a 1775 pro v with a stainless and 150 Merc. It would push 3 pas. 67 gps. Just feel my top end on this boat is way short at 42. I know I am heavier with this boat. Feel I should get about 50mph. Friend of mine has the same boat (2004) with a135 Merc. He runs at near 45. My brother has a 17 ft with a 125 Merc and runs 42. Both all three boats are set up with kickers and 24 volt.

Thank you very much

Dan

9/15/19 @ 1:27 PM
2014ranger+115
User since 8/7/17

See, now that tells us a lot.  You have a small range of 500 rpms to work with, that is the difference in your 5250 and 5750.  The middle would give you a range of 5500 to shoot for.  Based on approximately 1inch/400 rpms,  you would have to go down approximately 3 inches in pitch to raise you to about 5400 rpm.  Since you are at 21 pitch, you would need about an 18pitch.  Thats a good place to start especially since you have a heavier deep V boat.  Try an 18 and if rpms are too high then go to a 19 and vice versa.  Cupping or removing cupping can adjust your rpm a bit more if you like.  Just get it in that range and you will be good.  5500 would put you right in the middle of the recommended range.  Getting it to run about 5750 would allow you more torque to push heavier loads, you know...buddies, coolers, rods, anchors, kicker, full tank of gas, etc.  Go with aluminum for now.  You may be able to sell or trade your existing prop or keep it as a spare but take out the cupping if you do to raise your rpm,  Cupping adds about 2 inches of pitch, which I didn't mention but by now you probably figured out.  Once you get it dialed in then you can go to stainless as your primary prop,  They are more fuel efficient but you may not notice the mileage but you may pick up 1-2 mph which again equates to more speed because of effiency.    Stainless blades are thinner and stronger.  Aluminum blades actually flex a little under heavy use.  Dont believe it?  Remember that skyscrapers bend in heavy winds.  Your diameter on the 18 may go up to about 14.25.  You wouldnt notice unless you looked.  That brings us back to the "loading up the motor" factor.  Now you should pretty much have your answer to what prop to use, or at least get you very close.  By the way, where and what are you fishing for.  Great lakes fishing may keep you from hitting bottom with the prop, etc.

9/15/19 @ 12:22 PM
fuzzyfishin
User since 3/26/07

2 stroke

Wot 5250-5750

9/15/19 @ 12:24 AM
2014ranger+115
User since 8/7/17

FuzzyFishin, do you know what your actual operating range for that motor is?  I could not find that particular motor online without more info. Is it a 2 stroke?  Johnsons were make by Suzuki for their 4 strokes and later stopped putting the Johnson name on them.  Two strokes often rev higher as there are no valves to push or cams and lifters to move.  They usually make better power than counterpart 4 strokes however outboards are tuned a bit differently to make high rpm power but valves etc wear out a bit quicker.

9/15/19 @ 12:07 AM
2014ranger+115
User since 8/7/17

Speed is definitely a result of fuel efficiency.  The more efficient you are the faster you will go on the same power. The better use you make of your fuel the better your speed and mileage.  I disagree with ayeFeeshon the four blade prop because there are 2 ways to create thrust or load up an engine so that it wont freewheel all the way to destruction.    1.  A larger diameter prop will push more water but it will go slower because of a low pitch.  Look at the props on kicker motors from Merc and Yamaha.  the 9.9s have huge props and low gear ratios to create torque and push.  2. More pitch moves water faster but need a smaller diameter prop because you are pushing a lot of water with a big diameter.  More blades give better hole shot because they push more water with more torque via less pitch.  Try to find two similar props, one with large diameter and one with higher pitch for the same motor combo and you will see the higher pitch has less diameter and vice versa.  More blades also create more drag in the water.  Look on many smaller Hydroplane racing boats using small racing motors and you will see many. if not most using 2 blade props.  They are more efficient.  More blades balance out an engine better but I never could tell the difference.  Three blades are a great compromise.  They balance better than 2 blades but are faster than 4 blades.  Look at the 5 blade props and you will see they are targeting ski boats, etc.  They give a great hole shot and handling/balancing than the others.  They are huge diameter and low pitch, good for getting going while pulling a load but not good for top end or efficiency.  Your prop is the final gear in your drive system, like overdrive in your car.  Overdrive gives you both higher top speed and fuel effiency.  Todays cars are faster than older muscle cars with smaller motors mainly because they have overdrive and the older muscle cars dont.  You cant go fast with 4.11 gears unless you have overdrive but you will get a fast just when the light turns green.  Same with the boat and prop.  The further you travel on a drop of gas the faster you will also be.  I am not affiliated with Airmarine Propellors in Chicago but talk to Kathy or Chris.  They have been doing this for both planes and boats for longer than I have been boating (pre-1980) and know their business.  They helped me prop out my ranger, trying about 6 props in all.  My boat came over propped with a merc 23 pitch on it and wasn't good for anything.  The stainless lazer2 in 21 worked great.  The 20 was a re-man prop I bought from them and like that one even better.  I bought both props from them at the same time.  Good people to do business with.  They speak with authority and knowledge and Kathy's husband does the repairing, or at least he still was when I bought from them.  Dont go more than 3 blades for the best all around prop, especially if you are looking at mileage.  The best thing to get better mileage is to not push the throttle all the way down,

9/14/19 @ 8:09 PM
fuzzyfishin
User since 3/26/07

Sorry was out fishin when I posted and had a brain fart.

The motor is a 2000 175hsp Johnson 2str. Should get from 5250-5750 rpm.

As I mentioned not looking for hole shot or speed. Just want to run most efficient.  

Thsnks

  Thanks for your thoughts and time

Dan

9/14/19 @ 7:39 PM
ayeFeesh
User since 5/17/11

Didn't post your motor make and HP. Need to know that.


4200 RPM seems low for most motors. If I had to guess you should be looking for more like 5200.


I would drop to a 16 or 17 pitch prop - 4 blade. And your most fuel efficient speed will be around 3500 rpm. Find a marina or boat dealer that will let you test run props. Good luck.

9/14/19 @ 3:04 PM
2014ranger+115
User since 8/7/17

Props can get confusing so here you go.  There is no magic bullet.  You dont give much info but generally a 1 inch pitch up or down will result in APPROXIMATELY a 400 rpm change at wide open throttle (wot).  What rpm range should you operate in at a maximum and figure from there.  This is a for instance here, if your motor should top out between 5000 and 6000 then around 5500 would give you a good range to shoot for and be in the range recommended and still give you a good hole shot and top end.  At some point speed will not increase and rpm will come down, which is what you have now.  You may increase speed by going to a lower pitch prop but then again your rpm will increase.  At some point you will not gain mileage or economy as wot is still wot and you will be pumping the same amount of gas but not going any quicker.  Your benefit would be better torque and less time to plane, especially when you have buddies along.  Boats get heavier as they age too, You bring more gear and we all get heavier, etc.  The best way to maximize your mileage is to throttle back.  You can find online performance specs that include your engine and tell you what rpm your motor is most fuel efficient and run it there.  The fact is you may not like going that slow.  You can almost bet your life that your most fuel efficient speed is at idle and then somewhere around 3000 or 3500 rpm and it will be somewhere about the minimum it takes to keep you on plane.  You can have a prop shop remove the cupping on your prop and it will bring your rpm up and maybe your speed.  You may like it and you may not.  it may cavitate in tight turns.  It may just be a good spare prop.  A more powerful motor can spin a large prop easier thereby running at slower rpm and producing higher speed than a smaller motor at a given rpm.  Believe it or not, I had a 10 ft john boat with 5.5 hp that used the same amount of fuel on the chain of lakes as my 17.5 ft bass boat with a 150 on it.  The reason is that  little motor ran at 6000 going almost nowhere but the 150 ran at 6000 turning a 24 pitch prop.  but it saved me a few hours going where I was going.  The bigger boat was more comfy too.  Going faster is always more fun too.  The bottom line is start by figuring what rpm range you want to be in and use the 400 rpm/inch method to start.  You can find  gallon per hour specs etc on the internet.  It doesnt necesarily have to be your boat and motor combo.  You want to know how the motor runs at what rpm and then prop accordingly.  Your speed will be what it is.  You can prop for the lower rpm spec for torque or higher for lower rpm.  You may or may not see a speed change either way.  I have a 115 on my Ranger (duh) and get the same speed with a 20 or a 21. I like the acceleration better of the 20 but the rpm climbs a little more.  The 21 brings the rpm down with no change in speed per gps.

 If the best running prop you find runs a little high in rpm, then you can have the prop shop put more cup in the prop and it will bring down your rpm.

 It will also grip water a little better allowing more trim which may result in a little more speed or rooster tail.  It may allow you to raise the motor one hole notch which may result in higher speed and efficiency and cut down on rooster tail and porposing.  Watch your water pressure when raising the motor as you may not pick up enough water too cool the motor.  Raising the motor will somewhat slow a hole shot.  We all want the best of both worlds.  All you can do is keep tuning until you get what you want and after that you have to live with what you have.


DISPLAYING 11 TO 19 OF 19 POSTS
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