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2004 Volvo Penta SX prop 3-blade to 4-blade pitch?

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  • 2004 Volvo Penta SX prop 3-blade to 4-blade pitch?

    Bought a used '04 Four Winns Horizon 180 w/ 4.3GL a couple years ago and it came with the factory 3-blade installed and a spare 4-blade Quicksilver was given with the purchase that has never been used. The OEM prop is a 14.25x23 apparently (I assume it is the OEM prop), but the 4-blade is a 14x20. The OEM specs are 4600rpm max on this motor. The RPM gauge is broken but it has run good for 2yrs including some WOT runs and I suspect it is right where it needs to be w/ the 3-blade. However, I take several people out and gear and I want the power & potential fuel savings of the 4-blade (I read it can save fuel when towing and at cruising speed?)

    1.) Will the change from 23 to 20 be too much for the RPM's?
    2.) When changing props, is it ever okay to use a different size such as going from 14.25 to 14? Can I do this if I have the right pitch?

    I would really like to be close to the same speed as I can without going over the RPM max and from my limited research, I'd need to keep same size and just drop 1 size in pitch (not even sure if they make a 22 pitch for this outdrive?)

    Thanks for your help fellas!

  • #2
    Get a the Tach working, then try the 20, to me it sounds about right Extra Blade , 3 inches less pitch, about 4 - 5 mph lost. That actually lowers your Fuel Economy.
    Myself, I wouldn't run a 4 blade even with a Gun Pointed at me

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    • #3
      Could I run a lower pitch 3 blade if I don't exceed the rpm's? I just want something to help it move better towing or with a load in the boat...If I can do 40 I think I'd be fine with it...boat prob hits 45 tops as it sits...I have no idea how to fix the tach....a couple years ago I started a thread here and tired some stuff but I never resolved it...wish I knew what to do. Can I run a 14 instead of a 14.25 if i do decide to try to 4 blade?

      Tell me also why no 4 blade ever for you? thx for your expertise as always!

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      • #4
        Don't be very concerned about the Diameter, leave that to the Prop Engineers. How about replacing the tach? As long as you don't exceed the Max rpms there is no problem, Find out what your engine WOT range is, I think it is 4400 - 4800 but find out from Volvo.

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        • #5
          Can I just get any aftermarket marine tach that fits the hole and closely matches my other gauges? Or are there different ones from a wiring perspective? I would not know where to get an OEM tach and I'm sure it would cost a pretty penny for a "guess" that will be the true fix.

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          • #6
            A lot of Marine Tachs are Faria Brand. They have settings for a V8

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            • #7
              Hi
              first off, I’m almost sure tour rpm range will be 4400-4800 on your engine.
              second, I’d think that a 23” on the sx vp (if it’s the usual ratio I think it might be) is maybe verging on a little much for the boat, unless you run very light all the time.
              3rd, if you are indeed set up well with the 23” 3 blade as it is...going to a 20” 4 blade will see a serious drop in performance for sure. Apart from that...there aren’t many good reasons these days to have a 4 blade on a set up like that. Most good 3 blades can almost achieve the only up side of a 4 blade...and of course don’t suffer on efficiency or top end like the 4 blade will.

              lastly, I’m not entirely sure on this, depending on what you got with the 4 blade quicksilver prop...but it may well have a different hub kit that’s not suitable for your sx. Maybe it has had a suitable one supplied with it ?? I’d also add that a even pitch like 20” might be unusual for a quicksilver prop of that fitting spec. Not sure though.

              Comment


              • #8
                Thanks for the responses; it would seem to me that "if" I am running in the factory max rpm range with the 23 pitch 3-blade, that going to a lower pitch 3-blade may make the boat get out of the hole better, but then exceed the max rpm range. Therefore, I am wondering if there is a way to move to "any" prop (whether 3 or 4 blade) to give me more towing/hole shot/heavy load performance without exceeding the rpm range? At this point, I am okay with losing a little top end speed if the other objectives are met.

                The quicksilver did have some hardware supplied in a bag with the prop but i have not looked to see for sure if it is what all is needed to make it fit the VP SX. Sounds like a 20 4-blade may be too aggressive but the reason he told me he got it was to tow wake boarders better...not sure if he made his own purchase without enough expertise, or if someone that knew what they were doing sold it to him. But since he never installed it, that was never determined.

                EDIT:

                Using this link: https://turningpointpropellers.com/PROPWIZARD/ and inputting all my real world data it was recommending 15x15's and 15.6x13 etc....sure seems like a major difference from stock but I did input 6 adults and a few hundred pounds of gear and a full tank..."IF" this calculator (which uses your real boat make/model) is close to accurate, then you'd think testing the 20 pitch would be totally safe, but it is only 14" in size and the OME is larger and the recommended props from the calculator are even larger...I do not know about how the diameter of the prop comes into play and if it is okay to deviate from stock?
                Last edited by USA_boater; May 21st, 2020, 01:42 PM.

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                • #9
                  I eyeballed the clearance and there is no way a 15.5" prop will fit. I read the reviews on an updated version of the spare Quicksilver prop I have (except14x21 instead of my 14x20) on a review site and someone commented that his Four Winns H180 w/ 4.3 was perfect with the QS 14x21 so I figured why not try my free prop before i buy anything? I installed it and will test this weekend if weather permits. I already added this: https://www.stingrayhydrofoil.com/products/airo and it did make a difference in planing time & speed to stay on plane with little to no top-end loss...I sort of wish I had gone 1-piece but the holes are already drilled and now I am on to the prop...I want to be able to move some weight and have a smooth ride..top speed is less of a concern.

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                  • #10
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                    Hi. Just quickly, there is no way that a 15x15 or anything like it is going to suit your boat. Not sure but either the calculator is wrong or the info put in is a little off. You perhaps really need to be getting more info and accurate data and info. Like make sure you are happy with the tachometer and I really think your rpm range should be 4400-4800.
                    Anyway, despite all that and at the risk of taking stick for not playing it safe and demanding exact facts and data figures...I might be tempted to go out on a limb and tell you that with your 18ft boat and 4.3...coupled to a VP SX and assumed ratio of somewhere between 1.6-1.8...you won’t go far wrong with a good 21” stainless merc prop like a tempest, enertia or even a late model laser 2...of course with a suitable hub kit to match. I’d be confident enough in telling you that.
                    main thing is really trying to get accurate gps and rpm data when she is flat out and trimmed up as she is. Then take it from there...but if you were starting from scratch and didn’t even have a prop to start with...I’d be perhaps suggesting that you wouldn’t be far out going for a 21” 3 blade as mentioned above.

                    good luck.

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