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Which Prop? 40 hp Evinrude

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  • Which Prop? 40 hp Evinrude

    Running '62 evinrude 40hp.

    My head is swimming and I am in a daze with all the prop and pitch information.

    The problem:
    runs good at low speeds but at WOT it REALLY jumps in rpm's with ALOT less thrust. It feels like a spun hub but I have tried 3 props that are all alike and it does the same thing.

    The dilemma:
    Although the later models call for numerous sizes, the size in my parts book specifically calls for 10-3/8" diameter X 13-1/4 pitch.

    Has anyone heard of Propco Propellers?? They have really good prices and they swear up and down that I want a 10-1/2"X12pitch (I am running a fairly lightweight 1961 Red Fish 16' fiberglass closed bow Baylap).

    Also getting one clank at mid-range speed but I don't think it's slipping out of gear because I DO NOT lose thrust completely. Is this related? The folks at propco said there is an adjustment (but they want me to buy a prop first before they tell me).

    Thanks
    Shawn T
    WIchita, KS


  • #2
    Re: Which Prop? 40 hp Evinrude

    If you have the correct parts book for your motor, stay with what it says. That "clank" is something you should check into. First, check the gear grease in the lower unit. If it looks milky, you have water getting in there and that will need to be addressed with new seals. I doubt there is an adjustment on the shift linkage (but there may be) If not, the clutch dog is probably worn down and needs either replacing or "flipping".
    United States Coast Guard Officer #1172938
    Catamount Marine

    Comment



    • #3
      Re: Which Prop? 40 hp Evinrude

      Originally posted by Intermediate Mariner View Post
      Running '62 evinrude 40hp.

      My head is swimming and I am in a daze with all the prop and pitch information.

      The problem:
      runs good at low speeds but at WOT it REALLY jumps in rpm's with ALOT less thrust. It feels like a spun hub but I have tried 3 props that are all alike and it does the same thing.

      The dilemma:
      Although the later models call for numerous sizes, the size in my parts book specifically calls for 10-3/8" diameter X 13-1/4 pitch.

      Has anyone heard of Propco Propellers?? They have really good prices and they swear up and down that I want a 10-1/2"X12pitch (I am running a fairly lightweight 1961 Red Fish 16' fiberglass closed bow Baylap).

      Also getting one clank at mid-range speed but I don't think it's slipping out of gear because I DO NOT lose thrust completely. Is this related? The folks at propco said there is an adjustment (but they want me to buy a prop first before they tell me).

      Thanks
      Shawn T
      WIchita, KS
      Are you sure the motor is not cavatating, that is, is the prop too shallow in the water when the boat starts to plane?

      Comment



      • #4
        Re: Which Prop? 40 hp Evinrude

        Thanks for the replies guys.

        Yes the gear oil is milky but only after 3 trips to the lake- my prop shaft seal IS leaking because it had a double seal installed on the oil seal retainer so we left it (but I can see the oil leaking out from this point).

        The clank is I think the clutch dog slipping.... BUT I don't lose thrust and it may be just popping in and out. The parts I used were used (The best of 3 junk motors-those gears are expensive) but wear seemed minimal. I'm going to open it back up and have a look.

        Update on prop situation:
        I was using (according to number on prop PJ30) I believe a 10-3/8" X 12-1/2".
        ALSO: I cannot plane out no matter where the motor is set.
        It is fine in low to mid-range speed BUT as I increase to WOT, the mph stays the same but the rpm's go way up!!! I get no more thrust.

        I am estimating the boat at 1000lbs loaded down, although it's a 16' it's fairly skinny and short with only a 16" transom.

        So would my need be MORE pitch and possibly a bigger diameter? I believe I can run up tp 10-12/"X14" pitch on this motor.

        Any input greatly appreciated.

        Thanks
        Shawn T
        Wichita, KS

        Comment



        • #5
          Re: Which Prop? 40 hp Evinrude

          One more thing,
          This boat's hull is flat bottom in the back with v in the front (with a dip-down on the bottom of the hull in the front) - looks like a typical 1950's boat.

          Prop guy says to go with 10-3/8"X13-1/4" and no more under any conditions.

          And as mentioned earlier, I am running a 10-3/8"X12-1/2" currently and it won't plane out - just revs high and won't increase speed (doesnt lose speed)... it's like it's not turning enough water, does fine at low speeds.

          Comment



          • #6
            Re: Which Prop? 40 hp Evinrude

            Listen to the Propco guy. The 10 1/2 x 12 was the best prop for that motor on the average boat it was likely to be used on (16').

            I think your motor is cavitating (ventilating). How high are you running it? The anti-cavitation plate needs to be somewhat below the bottom of the boat with that motor.

            Comment



            • #7
              Re: Which Prop? 40 hp Evinrude

              Thanks FR.

              I pasted a photo below... as you can see the cav plate is right AT the bottom and not too much below it.

              Propco initially said 10-1/2"X12"... But after telling him (Peter) everything he thought maybe 10-3/8" X 13-1/4"...

              What are your thoughts?

              Thanks!

              Shawn

              Comment



              • #8
                Re: Which Prop? 40 hp Evinrude

                As far as the "clank" be sure the shift cable moves all the way.Most likely a warn dog though. The setup looks good. Is there a keel down the middle? Is it over size
                either width or depth.Is there a bailer hole in the bottom that might be disturbing
                the water in front or near the prop. It sure sounds like excessive slip or venting.
                Has the bottom been glassed or modified perhaps a little rough?
                See if you can find a 4 blade prop.You might see if a prop shop can add some cup.Is there any way you could lower the motor even if only 1/4" or so perhaps by removing some trim on the transom.To split gearcase does limit the height.

                Comment



                • #9
                  Re: Which Prop? 40 hp Evinrude

                  Thanks Steel.

                  There is sort of a keel... BUT... it end about 12" from the stern and there is a flat "pad", supposed to make it easy to plane.

                  Oversized? Not really, it's fairly narrow at 66" wide and shallow with a 16" transom.

                  The bottom was glassed on each side where original bunk boards made an indention in the bottom.

                  I cannot find a 4 blade prop for this motor.

                  On transom trim I used 2 pieces of 1/8" angle aluminum so the max i could gain is 1/4".

                  What will a "cup" do for me?

                  Thanks!!!

                  Comment



                  • #10
                    Re: Which Prop? 40 hp Evinrude

                    A 1/4" isn't likely to solve your problem but it might at least get you up to speed.
                    Is there a slight indentation(groove) in the bottom just forward of where it joins the transom? Also the grooves forward in the bottom could be causing turbulance especiually if they continue to the stern.Hard to tell how smooth it is;but if its kind of pebbly it might be causing problems.Did the prop ever work right?
                    Adding cup to the prop will help it grip the water,reduce slip.
                    Did you rework the transom? If you glassed the bottom and reworked the transom you may have added overall height to the transom.
                    There are 4 blade props out there Diameter will likely be bigger and pitch probaly low.
                    But diameter doesn't matter in this case(the more the better) and the pitch can be reworked a little.

                    Comment



                    • #11
                      Re: Which Prop? 40 hp Evinrude

                      Thanks again Steele.

                      It does seem to have indention just forward of the pad (where the back keel roller is) but that's how it was.

                      Don't really have any other grooves (some of that is stainage).

                      It IS indeed a bit "pebbly" though (I used epoxy bottomkote and rolled it on).

                      This is the first season on the water for me (this boat was a rebuild).

                      The prop I have is the one I got with the motor (10-3/8 X 12-1/2). As mentioned before my parts book says 10-3/8X13-1/4 but i thought that to be odd since the boat type matters too (plus all other models list several props but mine only lists one).

                      Boy, a cup sounds like a win/win situation.. are there any disadvantages?

                      In your opinion, is a 13-1/4 pitch enough or do I want ot try the 14?

                      Shawn

                      Comment



                      • #12
                        Re: Which Prop? 40 hp Evinrude

                        When "standard" prop sizes are suggested its based on the typical application.
                        10 3/8 X 14 is the highest pitch listed in the 62 brochure.
                        I think that would be for a pretty light boat.I think a 13 1/4 would work fine.
                        Once you get a grip you can adjust if need be.
                        Only dissadvantage to adding cup is it may lower rpm not a problem if revs were high in the first place. Explain your problem they should know where and how much cup to add.You might try smoothing the bottom finish a little.
                        My thoughts are that the down and dirty cure is probably to remove about an inch from the transom assuming it solves the problem then just use sticks add about 1/4" at a time to a point just before venting becomes a problem again.
                        As long as the clamps have a good grip you can finish the transom and just use the sticks to set the height.My boat has about a 1" stick holding up my 50 merc.

                        Comment



                        • #13
                          Re: Which Prop? 40 hp Evinrude

                          Well it's definitely pretty light. With motor off I can easily lift the stern off the trailer. I would say no more than 3 or 400 lbs max. The motor weighs 150. I added 1/2 ply floor. There is no way in the world that it weighs more than 700 lbs with a full tank. Plan to still add seats and bimini top but that's it. These problems all occured with 2 adults so I would say 1000 lbs at the most. Is that heavy?

                          Also boat is pretty narrow at 66".

                          Comment



                          • #14
                            Re: Which Prop? 40 hp Evinrude

                            Look again at the first photo! That hull has a NASTY hook in it which will affect performance. Before you go crazy with the engine and props, get the hull correct.

                            Comment



                            • #15
                              Re: Which Prop? 40 hp Evinrude

                              Thanks Frank,
                              That is how the hull is... the front drops down quite a bit. I would never imagine why they designed it that way... it collects so much water down in that bubble I had to add a second bilge pump in there.

                              Comment

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