Jump to content
  • GUESTS

    If You  want access  to member only forums on FM, You will need to Sign-in or  Sign-Up now .

    This box will disappear once you are signed in as a member.

  • 0

Another prop ??


WaveWacker

Question

Great post in the past on prop/pitch questions. Here is another quick one. A friend of mine is running an older 1890 Lund Pro V (Just had it refurbed, it looks great), and has that coupled with a new Yamaha 115hp 4 stroke. I believe he is running a 13" pitch Alum. prop on it (not sure of dia.). I believe the suggested "high end" rpm's is around the 5000-6000 range and he feels that it is over rev-ing as it is running over 6,000rpm when opened up (about 6300 I would guess). He also gas the same pitch SS prop. From what I can remember last fall the SS had even higher rpm's. That makes sense to me because there would be less flex in the SS, right? If a person is running to high rpm's with a 13" pitch Alum. prop would going to a 15" pitch SS be right or would one have to go even more (17") to get the high end rpm's to be right?

Link to comment
Share on other sites

4 answers to this question

Recommended Posts

  • 0

An 1890, I would say that this a older one smile.gif

The rule of thumb for pitch is, for every two inches of pitch increase you will loose 200 rpm. If he is running a 13 on that combo and getting 6300 rpm, I would really consider a 17 or maybe a 19 inch pitch.

I have a 70 on the back of a 17 foot crestliner and am pulling 5300 with a 17" pitch prop and that seems to just about right. Comes out of the water and on plane right now and cruises to 35 mph without any bogging or lugging.

Link to comment
Share on other sites

  • 0

The 115 four strke yamaha is supposed to operate at 6000 rpm at wide open throttle. I am actually surprised the stainless has higher rpm. Check the diameter of the two props and I bet the stainless has a smaller diameter but same pitch.

All other things equal a stainless should run lower rpm then an aluminum because of the increased cupping and greater resistance due to the fact that the blades don't flatten under heavy load like aluminum does.

Based on the info, I think a 15 would be fine. You want to get the 6000 rpm's at full throttle with the boat loaded as it would normally be...(full tank of gas, 3 or 4 people, gear, etc.)

Otherwise, lets say you get a 17 and run 5900 rpm at full throttle with just one guy in the boat and no gear at a faster top speed than the 15......All is good right.

Then you fill the tank and add 2 or three guys to the boat and suddenly at full throttle you can only get 5000 rpm and the boat doesn't plane out worth a crud.

You just have to weigh your options.

Link to comment
Share on other sites

  • 0

Oh I see, it is a matter of the alum flattening out more and not "grabbing" as much water. I was under the impression that the alum. would "open up" an grab more water at higher rpm's. I may be wrong on the SS running higher. I'll have to check with him on the diameter's. Makes perfect sense. I think what he is looking for is to not over rev. under normal weight conditions but still not go too large of a pitch that it speeds up his min. troll speed. Keep any more imputs coming in. Thanks.

WW

Link to comment
Share on other sites

  • 0

Wavewacker,
I also have a new Yamaha 115hp Four stroke. It's fitted with a Hustler 13.25" with a 17" pitch. I posted similar questions regarding dia. and pitch. Yamaha-motor.com under the accessories section answered a lot of my basic questions. They have a nice chart that shows some average speeds you can expect with different sizes and pitches of props. However I have yet to find out for sure if you can lower the dia. of a prop while increasing the pitch to try and increase top end speed. Or if that defeats the purpose. Anyway, just wanted to pass the website along.
STARMAN*

Link to comment
Share on other sites

Guest
This topic is now closed to further replies.


  • Your Responses - Share & Have Fun :)

    • FrankOcean
      My grandmother is a very old person, and she has had a real estate company for 20 years now, she has dedicated her whole life to it, so she does not understand much about technology and is looking to modernize her business, she is one of the few real estate companies that They don't have their own application, so I see myself in charge of finding a good software developer for real estate and that type of business. Do you know any professional or company that is dedicated to it?
    • BobT
      Don't forget about IP Lures just west of town about 2 miles on the south side of Co. 82.    I was out on Osakis last week for a couple hours. Picked up two walleyes, one about 13" and the other a fat 14-1/2". Also a couple northerns and a handful of perch.
    • Andre.y
      Of course, you shouldn’t even ask about this, because this is the responsibility of the executor of the order, that is, the employee who will create such an application. I think it will be stated in the contract of employment if there is one and then you don't have to ask for anything.
    • smurfy
      👍 awesome sauce!!!
    • CigarGuy
      Shallow. Got skunked tonight. Just got chased off by the weather. Last evening was the only time the last 4 times out I caught fish. Last even was light drizzle and calm water. Water warmed up about 3-1/2 degrees since the first time out.
    • Kettle
      Got into the cranes, 5 a piece this morning for two of us  
    • Fasterok
      It is very important not only to identify mushrooms by their appearance but also to understand whether it is useful or not, because now there are many poisonous mushrooms, and it is extremely important that no mistakes were made in the selection of such mushrooms. That's why I here https://www.mushrooms.online/mushroom-poisoning/ read a lot of interesting information about poisonous mushrooms and was able to understand more about it. I hope that I was able to help you and was really helpful to learn. 
    • TimothyBoolman
      Nice article
    • FrankOcean
      e-commerce applications always do wonders for any business so your idea is very good, someone here in this forum should be able to recommend you some good company that can help you develop the application, remember to ask them to review the application before launching it to the market, so that it does not come out with errors, if it has errors you will lose many users, good luck with your business!
    • FrankOcean
      With all that amount of guests you have, you need to create the application, yes or yes, it will facilitate communication between you and your clients, making it possible for you to answer each query, doubt and order that they ask of you, in addition to being able to charge them for your service with total comfort, try try to contact a company that is dedicated to developing this type of applications, although I cannot know exactly how much the creation cost will be, so try to have enough capital to spend
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Privacy Policy. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.