Results 1 to 16 of 16

Thread: 1985 Yamaha 40sk prop advice

  1. #1
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default 1985 Yamaha 40sk prop advice

    Looking for some advice on props for this motor. Ive got it on a 15ft alumacraft waterfowler. Looking at the YBS props as I have heard good things. Anyone have experience or can compare the yamaha oem YBS, a powertech scb3 and a cheap chinese knockoff stainless ybs clone? I am thinking somewhere around 14 or 15 pitch. Problem I am running into is the prop that is on the motor from the guy I got it is unmarked on the prop as well as no markings on the hub. Going to try and get a small tach ordered before I get too serious.

  2. #2
    Join Date
    Nov 2013
    Posts
    4,987

    Default

    Yamaha 16G

  3. #3
    Join Date
    Nov 2013
    Posts
    4,987

  4. #4
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default

    ive got a bone stock motor you dont think 16p is too big?

  5. #5
    Join Date
    Jan 2020
    Posts
    1,166

    Default

    I have bought two knock off YBS props from this ebay seller.

    Both times they have made a mistake on their end and sent me an extra with each purchase. I messaged them back and they said to just keep it both times.

    I cant guarantee that they'll send you two, but its worth a shot if you were to go this route and want a free extra prop.


    https://www.ebay.com/itm/26573050547...3ABFBMoJvp_utg

  6. #6
    Join Date
    Sep 2018
    Location
    Somewhere around 213
    Posts
    108

    Default

    15 ybs should be a good start. Having a tach realllly helps with finding a prop if you really want to find what’s best for your boat. But there is a guy on Facebook that sells ybs clones for somthing like 225 tyd his name is Nicholas David Metrajean out of Louisiana


    Sent from my iPhone using Tapatalk
    “My names Thrane Tuck an I don’t give a fuck” - T-bone

  7. #7
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default

    Is the YBS semi-cleaver style my best bet for a fishing/hunting rig? just trying to get a little more top end than what ive got now with this beat up prop. You guys are all very satisfied with a semi cleaver style prop on a jon boat? or do yall have fiberglass rigs with pads?

  8. #8
    Join Date
    Nov 2013
    Posts
    4,987

    Default

    As long as your rig is 42" wide or greater and you are not loaded down in the water to the rails, that's plenty of motor to run that prop. Now if you're putting three bubbas and a couch lab in there, thats another story.

  9. #9
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default

    My boat is a 1544 so we should be good then. Right now Ive just got my motor on a CMC tilt and trim plate. Thinking about ordering a 4inch vance manual jack plate when I order the prop. 8 inches of setback should give me enough room to jack it up and run the sandy bottoms of little pee dee without too much worry

  10. #10
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default

    Quote Originally Posted by FULLCHOKE View Post
    I have bought two knock off YBS props from this ebay seller.

    Both times they have made a mistake on their end and sent me an extra with each purchase. I messaged them back and they said to just keep it both times.

    I cant guarantee that they'll send you two, but its worth a shot if you were to go this route and want a free extra prop.


    https://www.ebay.com/itm/26573050547...3ABFBMoJvp_utg
    How recent has this happened to you?

  11. #11
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default

    Quote Originally Posted by FULLCHOKE View Post
    I have bought two knock off YBS props from this ebay seller.

    Both times they have made a mistake on their end and sent me an extra with each purchase. I messaged them back and they said to just keep it both times.

    I cant guarantee that they'll send you two, but its worth a shot if you were to go this route and want a free extra prop.


    https://www.ebay.com/itm/26573050547...3ABFBMoJvp_utg


    Alrighty I just ordered mine from this seller I will report back with results on number of props and prop performance. Thank you!!

  12. #12
    Join Date
    Nov 2008
    Location
    Scumter
    Posts
    21,795

    Default

    The prop you use is dictated by your hull style more than what is used for. Flat bottom jon boats generally do best with a semi clever blade shape. Even if the hull has a slight v in it they are still considered "flat bottom".

    Your tach will give insight on where to adjust. I'd start with the 15 pitch, but perhaps the 16 is best suited. It's a roll of the dice. You really won't know until you put the prop on and go run her.

    One thing to consider is that your motor, being a 2 stroke, will produce more power at a higher rpm. The rule of thumb is if you have a prop that pushes your boat well, assuming all other factors equal (manufacturer, model, blade shape, diameter, etc), going up 1" of pitch will reduce rpm by 200. Conversely, going down 1" of pitch will increase by 200rpm. It's not an exact science, just a starting point for some guidance.

    Another consideration is if your motor's rev limiter is disabled. If not, you might not be able to go over 6,200 rpm. If you disable it and the best prop you find runs 6,800rpm at wide open throttle then you're golden.

    Say you're running down the river with a minimum load at 6,800rpm, then duck season rolls around and you load up the boat with guns, decoys, shells, 2 fat friends, all their gear plus a dog, then next thing you know you're running 6,200 rpm. For comparison purposes, if 6,100rpm is your starting point, in the same scenario you'll be running 5,600rpm and you may find the motor not running like it should.

    Either way, it'll be one big science experiment that will require time, money and patience. If you get the right prop the first time around you'll be extremely lucky.

    Good luck and may the force be with you.

    Sent from my SM-G970U using Tapatalk
    [SIGPIC][/SIGPIC]
    Delta in a nutshell: Breeding grounds + small wetlands + big blocks of grass cover + predator removal + nesting structures + enough money to do the job= plenty of ducks to keep everyone smiling!

    "For those that will fight for it...FREEDOM...has a flavor the protected shall never know."
    -L/Cpl Edwin L. "Tim" Craft

  13. #13
    Join Date
    Nov 2013
    Posts
    2,705

    Default 1985 Yamaha 40sk prop advice

    15p ybs tops IMO. A 16 is a lot of prop for a stock 40. I would even start with 14p unless you only run by yourself with nothing in the boat. A 14p should be capable of 37-39mph without even touching the limiter, you won’t need a 16p unless 46mph is even halfway reasonable.

    My boat with a 59” merc runs 46-48 empty with a 16p and wouldn’t come close if it was stock 40hp. Matter in fact the tohatsu 50 on it before barely touched 42
    Last edited by Gone South; 09-28-2022 at 04:49 PM.

  14. #14
    Join Date
    Sep 2018
    Location
    Somewhere around 213
    Posts
    108

    Default

    Also Somthing worth noting is 50 carbs and tuner on that motor is well worth doing to get 10 more hp


    Sent from my iPhone using Tapatalk
    “My names Thrane Tuck an I don’t give a fuck” - T-bone

  15. #15
    Join Date
    Jun 2022
    Location
    The Independent Republic
    Posts
    526

    Default

    Update only 1 prop came in. Went and ran it and it drives like a new boat. Still not much faster as it wants to hop too bad to trim up and let her eat. Any advice on cavitation plate height/nosecone of the foot height in relation to the bottom of the boat? Right now my cavitation plate is probably 1.5-2 inches heigh of the bottom but the middle of the nose come on my foot is a good 3.5-4 inches below the bottom of the boat. Was also wondering about how you’re supposed to run the semi cleaver style prop. When I would get it trimmed out fairly high it would sound like it was blowing out but was still pushing the boat fine. Cavitation plate still submerged when running WOT though. Any advice appreciated!

  16. #16
    Join Date
    Sep 2018
    Location
    Somewhere around 213
    Posts
    108

    Default

    Gots to raise that thing up pit the propshaft about level with the bottom maybe a tad lower


    Sent from my iPhone using Tapatalk
    “My names Thrane Tuck an I don’t give a fuck” - T-bone

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •