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Prop confusion

Motor7Motor7 Posts: 4Member ✭✭
2006 PartyKraft 22', Yamaha F90 w/oem 13 1/4 diameter x17 pitch  prop = 22-23 mph with a moderate load @ 5200 rpm

My SIL ran across a rocky shallow and destroyed the above prop. So I have been reading and researching a replacement that might give me more rpm. Everything I read says going down in pitch will gain rpm. Top rpm of the F90 is 6K, so there there is room for improvement. 

So at a marina near the lake I found a Solas 13 1/2x15. Slapped it on and I got 19mph @4800 RPM...????  Entering my boat info into several prop calculators points to a 14x13 I hesitate on this as I think I will loose more speed and more rpm? So now I am confused and think I will just have the oem prop repaired......what am I missing here?


  • BoomerBoomer USAPosts: 311Member ✭✭
    Dale Hollow Lake Byrdstown Tennessee
  • Motor7Motor7 Posts: 4Member ✭✭
    Boomer, I did the Yamaha prop match and it also says a 14x13......I'm going to find a dealer that lets me try a pitch or three. I just can't figure out how the boat was running fairly good with the original 17 pitch on it. 
  • CRFCRF Posts: 229Member ✭✭✭

    have you added weight or anything on the boat that could cause drag? Altitude, 3 blade vs. 4 blade,  mmmmmmm.....

    18 ft. Sweetwater Sunrise (F) Pontoon  "Slice of Life" ; 40hp. Yamaha

  • Motor7Motor7 Posts: 4Member ✭✭
    No, we were at 330'  altitude with both props and identical loads....4 adults one child and a small soft cooler. Both props were 3 blade. I talked to a local Yamaha dealer today and he is recommending Yamaha props and they are willing to let me try a few out to find one that works. The Yamaha prop finder recommends everything from a 13.5 - 14 diameter to a 12-14 pitch. 

    Their prop finder does not ask length of boat or weight which is why the numbers are all over the place. Looks like real world "try it and see" is the only answer............

  • Motor7Motor7 Posts: 4Member ✭✭
    I have to ask.....Did Godfrey  test run their pontoons with different props and if they did where can I find that information?
  • BoomerBoomer USAPosts: 311Member ✭✭
  • carguybillcarguybill USAPosts: 34Member ✭✭
    Good article, Boomer. So, according to the article, our best bet for all round performance is a big eared 4 blade prop. I wonder why, if this is the case, the new engines aren't supplied with this configuration or, at least, offered as an option?
    Bill Brown
    Sweetwater 2086BF
    Home: Coshocton, OH
    Boating: Cold Stream Pond, ME
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