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  • New boat prop question

    Hello all, I have a new to me 92 stratos 274 fs with a 90 evinrude crossfire. The porp on the boat looks like the original aluminum 3 blade 13 3/8 17 prop. I have ran the boat by myself GPS speed of 35 and with the family GPS speed of 33. I am turning 4900 rpms. The motor runs strong and it gets on plane quick with just me in the boat and a little longer with the kiddos. I tried to play with the prop calculators and it seems I should be going faster with this prop. I am gonna replace the prop my question is, would you stay with the same size or start playing with the pitch. What would you do? I am leaning buying the same prop but stainless and see what happens then possibly buying another depending on performance. My main goal is to use this for fishing and getting to hunting spots in the fall but the kids also like to go out sometimes so another prop for tubing would be in order. Thank you all for reading this wall of text!

  • #2
    welcome aboard

    first, weigh your 28 year old boat and compare it to published specs

    many early 90's bass boats were made with questionable quality and many are waterlogged

    per the following

    http://boatspecs.iboats.com/Stratos_...92/bp/66b89337

    your boat should weigh 1375 empty. add motor at 320 and what ever fuel you have at 6.82# per gallon, then add the weight of your trailer (about 900# for a single axle), then compare to what you get on a scale.

    Agreed your motor should be turning more RPM's maybe make sure its running 100%

    also, you may want to look at a bigger motor. that boat is rated for 150hp, and with a 90 may be a bit under-powered
    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

    Past Boats
    1970 Wooster Hellion - Merc 9.8
    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

    What’s behind you doesn’t matter.Enzo Ferrari

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    • #3
      Thank you for the response. I agree the motor small for the boat. I will have to get it to a scale (great idea). The motor seems to be healthy but I haven't done the compression check yet or look at the ignition side. I am a heavy equipment mechanic so motors are not a issue for me but boat motors are a whole new endeavor for me. I also am not expecting to go much faster it just seemed a little off to me. It sucks trying to get a baseline of what it is supposed to do vs what it is doing to see if I have an issue somewhere. I guess this is boating lol.

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      • #4
        An engine mounted too low can cause up to a 20% reduction in speed and fuel economy. That should be corrected before even considering the prop. So check that first.

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        • #5
          You should make a wot test on flat calm water cond as "usually will be loaded" say family oriented, 2-3 up, whichever, not lightly loaded though with current prop, 4900 wot rpm seems very low, that motor should rev somewhere 5.0 to 6.0 K ? Need to know exact wot rpm range factory stated before attempting playing with different props and their pitches.

          Happy Boating


          Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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          • #6
            See rider, according to my book the rpm range for that motor is 4500-5500. The first time out was very calm water wot at 4900 rpm going 35 mph (gps). The reason I am going after the prop is because it is an aluminum and the edges are kinda in rough shape. I will try and get a pic. Uploaded of it. I will probably get a stainless prop in the same pitch that is on it and see what happens. (I want to switch to s.s. anyway). I need to bring some tools home from work to go through the motor and measure the motor prop depth.

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            • #7
              Your speeds aren't bad for an 18ft with a 90. As mentioned you might have a few pounds of Ballast.
              You are probably propped for best Top Speed right now.
              The 90 makes it peak HP a bit below 5000 rpm. and dropping pitch to get it to 5500, will result a loss of 1 or 2 mph. It will result in better holeshot. Any higher than 5500 and the HP really falls offs.
              Any imperfection in a prop blade will negatively affect its efficiency. How much? depends on the damage.

              Switching to a SS is no guarantee of more speed, the only Guarantee is the higher risk of Damage to the internals of the gearcase when the prop hits something solid

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              • #8
                I was going to switch to a stainless prop because my in laws who fish the same lake suggested I do. Their are allot of trees in mark Twain lake and they said if i run aluminum that i risk breaking a prop. if I hit a tree. The way I am reading/imaging it is their will always be a weak link if I do hit a tree, I guess it would be cheaper to replace a prop instead of a lower unit rebuild.

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                • #9

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                  • #10
                    This is how the prop looked/looks when I bought the boat

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                    • #11
                      Sign up today
                      TF,

                      You're right next to middle wot rpm range "as loaded" and it's the max top speed that motor should achieve. If you're happy with the hole shot leave that prop alone. If wanting a little help from my friends send that prop to a prop shop and have it repaired and repitched 1/2 size off to a 16.5 pitch, will improve the hole shot.

                      That motor is OK while you don't add to many extra boaters to the equation, has a MPH speed limit it will go while at 4900/5000 wot rpm.

                      Happy Boating


                      Sea Rider 320, 380 Sibs, 450 Rib, 2 Strokes Tohatsu 5,18 & 30 HP Proud Smokers

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