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Thread: Prop suggestions

  1. #1
    Join Date
    Jul 2006
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    Raystown Country, PA
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    Default Prop suggestions

    I have a customer who found a super clean 1984 model Evinrude 90 and put it on his 24 foot pontoon. Maiden voyage went OK with 5100 RPM and 23 mph for WOT numbers. It is blowing the prop out at WOT quite a bit, especially running into the wind. I know some of you guys have had these over the years and Malcolm probably put dozens on. Can anyone recommend a prop to try to help with this, a "pontoon specific" type of prop. I'm not sure what is on it now, he is going to get some numbers off it and let me know, I'll update here when I know.

    It's a 20 inch motor sitting on the transom and trimmed down against the pin in the bottom trim hole.

    We are going to try a whale tale, and I have the wedges that will kick the top of the motor out 5 degrees if he wants to try them.

    Wea are open to all kinds of suggestions.
    2006 Forester 19 Fish
    1990 Mercury 50 ELPTO
    1983 Sea Nymph FM171 Striper
    1985 70 HP Johnson

    Raystown Country, PA

  2. #2
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    Jul 2006
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    Michigan Wheel pj90 13x17 on it now, 1989 Lowe 240

    Thinking about the factory 13.75x15 for a replacement pn 391198

    If you know of a better option, please sound off.
    2006 Forester 19 Fish
    1990 Mercury 50 ELPTO
    1983 Sea Nymph FM171 Striper
    1985 70 HP Johnson

    Raystown Country, PA

  3. #3
    Join Date
    Oct 2006
    Location
    Denver, North Carolina
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    3,468

    Default

    17p is too big. I run a 15x15p Enertia on our 22rl with a 150 Honda. A 24 footer with a 90 I would think a 13p. What's the redline for that motor
    Carl & Suzi
    Denver,NC
    2007 Bennington 2275rl tri-toon
    150 Honda 15x15p Enertia
    Power assisted steering
    Beautiful Lake Norman
    Pleiku Vietnam 1971
    Agent Orange

  4. #4
    Join Date
    Jun 2004
    Posts
    6,114

    Default

    When you run that much pitch, it will for sure blow out. I think Carl is right on with the 13" pitch. I think the RPM range is 5250-5750 and I would prop it toward the high side with a light load.
    Rick


    2007 Bentley 200 Cruise
    2007 90 Merc. 4 stroke
    St. Louis/Lake of the Ozarks

  5. #5
    Join Date
    Jul 2006
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    Default

    I poked around out in my shop and found a 391198 OMC prop, it's not beautiful, but it's paid for, so we'll have a 15 to try. I'll post results then we'll make a decision on what to buy. Thanks guys.
    2006 Forester 19 Fish
    1990 Mercury 50 ELPTO
    1983 Sea Nymph FM171 Striper
    1985 70 HP Johnson

    Raystown Country, PA

  6. #6
    Join Date
    Jan 2012
    Posts
    694

    Default

    Good morning
    Have a 4 bade 15 pitch or 3 blade
    that's my take.
    Malcolm ( Goofy )
    TAP Fins
    8525 Sylvan
    200 H O E Tec




    " Keep a fire in your heart and a smile on your face, for you never know when your leaving this place"

  7. #7
    Join Date
    Feb 2014
    Location
    Boat at Lake of the Ozarks Missouri
    Posts
    485

    Default

    Guys, I'm with Goofy on this one.

    I've had some experience with the 4 bladed props and love it.
    No blow out in the turns at mid to higher rpms. Remember though a 4th blade will
    drop the rpms by about 200 - 250 and the pitch by about 1 inch.

    If you go with the 15 pitch, do the 4 blade, you will love it.

    PS - better hole shot also for tubing or pulling 1 skier.
    Last edited by Captain Tony; 09-26-2018 at 12:21 PM.
    Captain Tony
    2005 Summit by Triton - 220T Platinum 3Log
    2005 115HP Mercury Optimax - 228 Marine Master Trailer
    St. Louis & Lake of the Ozarks, MO.

  8. #8
    Join Date
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    Default

    He put the old 15 I had on and it got much better. Rpms dropped to 5k and it did not blow out as much. We are looking around for a 13 now, hopefully it will dig in better yet, but allow the revs to come up a little. The 90 is pushing the 24 footer at 26 mph, with just him and his wife.

    Any recommendations for a specific prop? There are lots of 4 blade 15s, or 13s, none of them is cheap and he just wants to buy one time.



    Thanks all.
    Last edited by Moser; 09-27-2018 at 04:30 PM. Reason: Really can't type with the phone. :)
    2006 Forester 19 Fish
    1990 Mercury 50 ELPTO
    1983 Sea Nymph FM171 Striper
    1985 70 HP Johnson

    Raystown Country, PA

  9. #9
    Join Date
    Feb 2014
    Location
    Boat at Lake of the Ozarks Missouri
    Posts
    485

    Default

    Larry, have your customer Go to mercurymarine.com.

    Find the prop selector tool. I'm sure Evinrude, Yamaha and Honda also have such an online tool - I'm just more familiar with Mercury.

    Fill out the on-line questions, have the boat weight numbers including gear, gas, passengers, etc. etc.

    Decide what you want to use the boat for. Input the current prop specs including WOT RPMs and speed.

    Choose 4 blade and it will tell you what Diameter & Pitch will give you the desired results.

    Remember the rpm loss with a 4 blade from a 3 blade and dial in the diameter that will get you into the sweet spot of the engine recommended range.

    If you know a local dealer who sells props, and promise to buy from him, (instead of mail order) at a fair price; then they may let you try out a few props to find your desired numbers.

    You may even have to sacrifice a mile or two on top end to get the right pull and WOT RPMs.

    Remember also you don't want to run all the time at WOT but you need the engine to develop the best HP & Torque in the WOT range.

    Finally, horsepower is not always the answer - torque is the pulling power you want.

    It's starting to sound like a 13" 4 blade is the right ball park.
    Last edited by Captain Tony; 09-26-2018 at 11:31 AM. Reason: Added comment
    Captain Tony
    2005 Summit by Triton - 220T Platinum 3Log
    2005 115HP Mercury Optimax - 228 Marine Master Trailer
    St. Louis & Lake of the Ozarks, MO.

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