Thinking of 4 blade for my Yam 25.. Any size recommendations?

Discussion in 'Prop Shop' started by Salty_South, Dec 5, 2010.

  1. Salty_South

    Salty_South Well-Known Member

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    Just got the jack plate on the Classic and may need a little more grip to get in the skinny water. I have been reading that 4 blade is the way to go. I am currently running the stock 3 blade 9 7/8" * 11 1/4 prop on my Yamaha 25 2stoke. My RPMs (no tach though) sound too high WOT.

    What size would you guys start with for the 4 blade? Anything else I should know before purchasing one?

    Thanks very much in advance!
     
  2. swaddict

    swaddict Thread Killer

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    It would help if you installed a tiny tach to get your rpm's. It's very important with choosing a prop. My old man is running a 3 blade powertech (with a decent amount of cupping) on his cc classic with a 4 stroke yammy, I'll check with him. He also has a cmc trim and tilt and that helps the boat run a little swallower.
     

  3. firecat1981

    firecat1981 BBA Counselor

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    Get, or borrow a tiny tach from someone, if not you'll end up buying 3 different props to get it right.
     
  4. Flyline

    Flyline Won "Do More With Less" Award!

    I had a gheenoe classic with tomC electric jackplate and a yamaha 25hp 2 stroke with 4 blade polished s.s prop 11" pitch heavly cupped prop. I only use this prop to ran shallow. With jackplate down it ran 5700 rpm at 27 mph, halfway up 6000 rpm at 29.5 mph, all the up with half prop out of the water at 6200 with half or more throttle at 23 mph.

    Its best to have a tinytach to moniter your rpm so u wont blow your motor up when jacked all the way up and then make sure your pee hole is peeing while running shallow.

    Hope this helps
     
  5. Salty_South

    Salty_South Well-Known Member

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    Tiny tach on order! I will report RPMs as soon as it arrives. Do I record RPMs at full throttle?
     
  6. cutrunner

    cutrunner Cert. Yamaha technician

    yea, full throttle
     
  7. The_Skiff_Shop

    The_Skiff_Shop Well-Known Member

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    The common oversight I see on this board is recommending a pitch or "size" without regard to blade design. All props are not created equal and the reason I stick with one manufacturer and specific blade designs. This allows me predict the results when making changes. Otherwise it's a crap shoot.

    That said, Power Tech SRA 4 blade in either 11 or 12 pitch depending on load with heavy cup should be the ticket with the jack plate. A super heavy or tow boat may step down to a 10 pitch with the same cupping.



    as always, just my .0000000000002.5 sense
     
  8. cutrunner

    cutrunner Cert. Yamaha technician

    very true, what he said. pitch is only the half of it. do you need transom lift, or bow lift? theres many things to change , pitch, cup,rake, camber,etc etc an accurate description of your boat and how its running at wot and a good prop shop can amaze you
     
  9. Salty_South

    Salty_South Well-Known Member

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    Well once I get this tach in the mail I'll have to go and try some out. I'll stick to the same brand so I can tell the difference; good advise!
     
  10. Salty_South

    Salty_South Well-Known Member

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    Just got the tach in the mail. I'm not sure what degree to set it to though. 360?
     
  11. Salty_South

    Salty_South Well-Known Member

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    Nevermind, tach didn't work. They are sending the one with the filter. Nice people over there. Hope the new one works!
     
  12. Salty_South

    Salty_South Well-Known Member

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    Still, great customer service but no read. They sent me the TT2AK with the filter but it still didn't work. They said they will send me another with a stronger filter. Or should I just try another company?
     
  13. robwill54

    robwill54 I Love microskiff.com!

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    I just picked up a '99 Whipray with a 25 Yamaha today. It is propped with a PowerTech SRA4 with 12" pitch, no jackplate. No tach so I have no idea what she turns but seems to perform well, and this is the original prop. Hope to photo tach it tomorrow to check RPM. Good luck with your quest.
     
  14. Salty_South

    Salty_South Well-Known Member

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    Thanks Seabob, I never did get my RPMs either so I can't say what I need but I was thinking that 4 blade 12" pitch would be perfect. I'm gonna see if I can find a used one on the web. Thanks for the the advise.