• If this is your first visit to the iboats.com Boating Forums, be sure to check out the FAQ. To post a question or comment, begin by signing up. To start viewing messages, select the forum that you want to visit from the selection below.
  • ALL iboats Forum Members and Guests:
    To show our appreciation for your participation in the Forums, we're offering an exclusive Forums-only discount good for an additional 5% off your iboats.com order for a limited time.
    To redeem, simply call our Customer Service Team at 800-914-1123 (Open M-F, 9am - 8pm Eastern Time) and mention the Forums 5% off discount. Offer excludes engines, trolling motors, and electronics.

Announcement

Announcement Module
Collapse
No announcement yet.

Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts


  • Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

    Hey All,I Just bought A 2006 Lowe FS175 w/2006 Mercury 115HP EFI 4-Stroke..It came with a 13x19 Aluminum Prop. I am looking at possibly purchasing a Stainless Steel Prop in the near future.I understand the pitch of the prop, and will probably keep that at 19" Pitch... What I don't understand is the Diameter of the prop? When looking for props, i see many different size diameters available.What difference will the diameter make? For example, If I were to go to a 12-1/4" diameter, or a 14" diameter, and stay at the 19" pitch, what difference would either of those diameters make?Thanks,-TheChad
    2006 Lowe Fish & Ski (FS175)
    -Mercury 115HP EFI 4-Stroke
    --Mounted 3rd Hole From The Top (Middle Hole)
    -Mercury Vengeance SS Prop (16 Pitch)
    -Lowrance LCX-26C HD


  • #2
    Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

    The larger sounds like it's a larger class prop used on MerCruisers and V-6 outboards. In a given class, you'll see the diameter decrease as the pitch increase. That's to keep about the same surface area accross the range for that class. Diameter within an inch or so doesn't make nearly as much difference as the pitch.
    Hey, Have you seen? They make Really Cool life preservers nowadays.
    So "Looking Dorky" is no longer an excuse for not wearing one.

    Comment



    • #3
      Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

      Going from a 12-1/4 to a 14 inch diameter prop means you've stepped out of the range of engines that prop was intended for. Chances are the two props are for two different prop shaft sizes. Generally there will be less than an inch difference in diamter in the entire range of props for a given engine. A 12-1/4 x 15P is one popular size for a 50 HP Evinrude. The next higher pitch is 11-3/4 x 17P. Even if you did find a much larger diameter prop that physically fit the engine, chances are it would hit the torque tab or the AV plate. Also, unless you make some WOT runs to check RPM and speed with the current prop, you don't know what you need.

      Comment



      • #4
        Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

        The prop that came on the engine is a 13x19... My question was what different would it make if it went from the 13x19 to a 12-1/2x19, or from the 13x19 to a 14x19.. In a stainless steel.I was just curious, 13x19 is available in stainless steel, so i could easily keep the exact same size, I was just curious what would be different if I changed Diameter...I havent taken the engine over 3500 RPM @ 25mph, I only drove the boat for about 10 minutes on the lake..Thanks,-TheChad
        2006 Lowe Fish & Ski (FS175)
        -Mercury 115HP EFI 4-Stroke
        --Mounted 3rd Hole From The Top (Middle Hole)
        -Mercury Vengeance SS Prop (16 Pitch)
        -Lowrance LCX-26C HD

        Comment



        • #5
          Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

          Chad, the prop you will need will be determined by wot and performance needs..Generally when going up in diameter you lose RPM unless you are willing to raise the engine to get the Rpm back and lose some drag..this is maximizing the set-up. Smaller diameter in a given pitch is used mostly on non-surfacing applications, and tends to be (in most cases) a bit slower, except for very light boats, where you find small dia. and large pitch.

          Comment



          • #6
            Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

            walleyehed: with a 13x19 Prop, at WOT trimmed up, I am at 5000 RPM.. According to Mercury, my 115HP 4-Stroke has a Redline of 5000-6000 RPM-TheChad
            2006 Lowe Fish & Ski (FS175)
            -Mercury 115HP EFI 4-Stroke
            --Mounted 3rd Hole From The Top (Middle Hole)
            -Mercury Vengeance SS Prop (16 Pitch)
            -Lowrance LCX-26C HD

            Comment



            • #7
              Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

              It needs to be well broken in, but 5000 ain't enough...that 4-stroke needs to be near 6000 to develope the power it's rated at...well, actually, it's rated at 5500, but they do best above the 5500.This is VERY typical of a dealer set-up.If it were mine, I'd opt for 2" less pitch which will gain between 600-800 RPM due to the powerband, and then raise the engine a hole at a time until I got close to 6000RPM.Load the boat with people and gear and you will be in engine destruction mode the way it's set up now.Alot of dealers need to go in for some serious training....

              Comment



              • #8
                Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                You said raise the engine a hole at a time, but it's power trim....So you suggest a 13x17 prop?With 4 people and gear in the boat, it does take a little bit to get the boat up to speed and on plane, with 2 people, it jumps on plane in just a few seconds.The engine has only about 6 hours on it, so It's not even completely broke in yet...-TheChad
                2006 Lowe Fish & Ski (FS175)
                -Mercury 115HP EFI 4-Stroke
                --Mounted 3rd Hole From The Top (Middle Hole)
                -Mercury Vengeance SS Prop (16 Pitch)
                -Lowrance LCX-26C HD

                Comment



                • #9
                  Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                  When I say raise the engine, I mean on the transom, not trim-n-tilt.I'm saying a 17 pitch yes, not a 13X17...don't get stuck on this diameter issue..it may be a 13-1/4X17...or maybe a 13-1/2X17...doesn't matter if it's made to fit your engine.

                  Comment



                  • #10
                    Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                    Is it possible that the engine is just to low on the transom now with the 13x19 prop?Is there a certain measurement as to how high/low the engine is suppose to sit on the transom?If all the sizes you mentioned are available to fit my engine, is there a pref as to which one?Thanks,-TheChad
                    2006 Lowe Fish & Ski (FS175)
                    -Mercury 115HP EFI 4-Stroke
                    --Mounted 3rd Hole From The Top (Middle Hole)
                    -Mercury Vengeance SS Prop (16 Pitch)
                    -Lowrance LCX-26C HD

                    Comment



                    • #11
                      Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                      FWIW...I have a 2003 Procraft 180 Combo with a 2004 115 4-Stroke. It came propped with the Black Max 13x19. At normal load, WOT, full trim I could only turn 5400RPM. I purchased a Turbo 2+2X, 13 1/4x18,my engine is mounted in the stock 2nd hole from the top. With this Turbo, I gained tremendous holeshot, WOT is now 5700RPM, but I lost about 3 MPH due to the 4th blade addition. After that test, I had the engine raised up one hole on the transom, now I am turning 5900RPM @ WOT, gained back my 3 MPH, plus 2, so now I am 50MPH, 5900RPM at WOT, gained a little more in holeshot, and improved my gas mileage. It is like a totally different boat now.

                      Comment



                      • #12
                        Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                        hmm... That's good to know.. Mine is only an aluminum boat, so if you are gettin 50Mph, I should be pulling more than that (Lighter)...I wonder if the transom adjustment is something that would be covered under the warrenty?!I Think I will start by just raising it up 1 hole on the transom, see what that does for me, then look into a different size prop...-TheChad
                        2006 Lowe Fish & Ski (FS175)
                        -Mercury 115HP EFI 4-Stroke
                        --Mounted 3rd Hole From The Top (Middle Hole)
                        -Mercury Vengeance SS Prop (16 Pitch)
                        -Lowrance LCX-26C HD

                        Comment



                        • #13
                          Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                          Hear me chad...Raise the engine until it slips or blows out...then Lower 1 hole-THEN prop for the set-up if you're leaving the engine mounted to the transom.The procraft has a pad and your aluminum will never get the performance...the weight isn't the issue...you have no pad, just like mine, it will be slower than those that do.

                          Comment



                          • #14
                            Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                            What do you mean by pad?Slips or blows out at what trim? all the way down?I am not really worried about the speed, I'd be happy with a better holeshot, and better fuel consumption, 42mph is plenty for me..Thanks,-TheChad
                            2006 Lowe Fish & Ski (FS175)
                            -Mercury 115HP EFI 4-Stroke
                            --Mounted 3rd Hole From The Top (Middle Hole)
                            -Mercury Vengeance SS Prop (16 Pitch)
                            -Lowrance LCX-26C HD

                            Comment



                            • #15
                              Re: Prop Diameter & Pitch Questions - 115hp EFI 4-Stroke

                              Pad is a flat surface, usually narrow smack center of the hull that the boat gets up on at high-speed reducing drag even farther...you and I don't have that feature built-in to our boats.The idea of raising the engine is for a couple of reasons..#1, we get the gearcase up some, eliminating a bit of drag, and by reducing drag we pick up a bit of speed. #2, we get the thrust-line closer to the bottom of the hull (the distance of parallel between the 2 becomes less) and this usually aids in hole-shot and acceleration. If we increase in all of these areas, we've increased the over-all efficiency, which means less effort from the engine at the same speed which increases fuel economy...it's a win-win.Proper set-up is the only way we can maximize efficiency...I know you'd like the better fuel economy, hole-shot, AND speed just because it's there..

                              Comment

                              Working...
                              X