15 pitch prop maybe a little too much for the 40 hp and it couldn't get the revs up enough to go faster? Propeller physics confuse me usually, so it was nice to see these 2 comparisons vids. Definitely sounded like the 3 blade 15 pitch wasn't revving as high as the 4 blade 14 pitch. That was just using my "ear tachometer" though to compare the sound! :)
Ears are pretty good, I heard the same. I'm sure the three blade would be better in a 14. He did say the boat is heavy, perhaps the 4 blade made better of the weight.
Well that's not a surprise. When going from a 3blade to a 4 blade and keeping the same revs, you go down 1 or 2" in pitch. That means that the 14" 4 blade will be like the 15" 3blade but with more grip or less slip rather. Hence the better performance of the 4blade. Also it's stainless which means thin rotors and even more grip since the slip factor will be less compared to a "soft" aluminum prop.
3 blades are for top speed, 4 blades are for torque and power at the mid range. You will NOT go faster with a 4 blade propeller. But you will have quicker planing, easier plane sustainment, especially in the corners or rough seas.
For blades stainless prop on my 425 HO Mercruiser good performance, but much corrosion on the stern drive, check your sink anodes, special anti corrosion paint on my stern drive
You would think a 15 pitch would go faster but you may have not reached 6000 RPM and that matters just as much . 4 blades are awesome on Aluminum boats
I have a 16x42 Grumman and its rated for a 50...i have a 30 on it and the fastest its been is 32. I imagine with a 50 she would hit38 or 40. Maybe 42. (Wich honestly would be scary fast in that boat). But i have the Same deal as your boat. Unlderpowered but gets the job done. I imagine your boat needs a 75hp to get what you want. But honestly I justlearned to be happy going a little slower
There is not much choice on the market. 10 pitch standard prop should be fine. If you want to try how fast your boat can go with your motor try to find 11 pitch. I never seen steeper pitch prop for your motor . 10 pitch for your boat I think is good all around
Vojo, Do you use 70:1 fuel ratio on all of your premix Yamaha outboards? I have a 2001 15hp Yamaha, of course it states 100:1 . I noticed that at 50:1 it runs a little rougher. I like your thinking of running 70:1. Seems like a happy medium. I enjoy all of your videos. Bud from Powder Springs Ga.
I've been watching your vids I subscribed to your channel I got a 1991 6 up 2 stroke Yamaha just like yours in the video a good while back I'm having trouble with it and can't find no answers I'm no mechanic really but when it cranks idles great when I put it in gear and take off it runs fine a few mins then just dies like it's running outta gas does same thing if I just drive it above idle dies like it ran outta gas let it set a few it cranks up runs fine does same thing all over again any ideas I just bought the Jon boat and motor a month ago please help I'm lost it's getting gas to carb I know that much you think it's the float in the carb or what it's like the bowl runs outta gas let it set a few mins I guess the bowl fills back up run it a few then dies I'd truly appreciate any info thanks
Take your petrol tank lid off and test again. Maybe the lid seals and does not breathe air. This will cause vacume in tank and restrict fuel flow to carb.
May be pointless since you said that fuel is flowing to the carb but does the priming bulb get hard and stay hard while the motor is running? I only post this because I was having a similar problem with my two stroke merc and all it needed was a new priming bulb. 12$. I am guessing you have probably already ruled this out as you have been in the carbs but it was what happened to me. Good luck to you.
15 pitch is too much. You need to check your rpms. You should be running a 12 or 13. The 4blade should be 12 pitch . 3 blade 13 pitch. The 15 pitch is for a 50hp motor. These little outboard are prop sensitive. I can remember a guy had too much prop on a 50 hp motor i convinced him to move down 3 inches in pitch. Runs perfect
Also without power trim its best to sacrifice some top end for cornering and lift. If she spins up on turns. Tuck the motor in a hole. A boat like this you should be able to turn Full lock at 25mph and not ventilate to bad
I am in the propeller Sales and Repair business... Interesting results you got.... In most cases that three-blade propeller should have been a couple miles an hour faster than the 4 blade but as you have noticed what should happen does not always happen. 😁
Hello prop doctor I have a 50hp Johnson outboard I want to buy a new prop for my outboard but I don’t know what I should pick some one told me to check rpms but my rpm reader is broken what do you suggest
@@gboyzathletics4090 you really need to have a accurate tachometer and accurate speedometer or these days you can use a GPS app with your smartphone because most boat speedometers are not very accurate and most of them show faster than you are actually going.... You need to get some kind of a Baseline and it's more important about the RPM then about the speed although that will tell you how efficient your prop is when you can compare speed in RPM numbers.... The right thing to do is have the pitch of propeller that lets your motor run right at the maximum recommended RPM at wide open throttle.... once you know this number then you know whether you need to go up or down in Pitch as every one inch of pitch will normally change your RPM 200 to 300.....
Hey propdoctor, I got one for ya... how can you figure out pitch of a prop if it’s not stamped or marked? Took a 4 blade off a ‘62 Evinrude lark iv 35hp, the stock prop is a 3 blade P13 or 11, I forget... anyways, I wanna try the 4 blade on my ‘62 28hp Evinrude speeditwin. I know it fits cause it’s on there right now, but I can’t find any numbers on it and I know it’s not the stock prop. More pitch means more twist to the blades right, less pitch means they gonna appear flatter, when viewed from the side... any way to measure at home withou specialized equipment?
@@TheFrogfeeder there really is no way to measure the pitch of a prop Without a pitch gauge... what the pitch actually means is that is the distance in inches the propeller is trying to move forward every Revolution. So are you higher pitch prop will go farther every time it turns than a lower pitch prop and yes a lower pitch prop the blades will look flatter when viewed from the side compared to a higher pitch prop
