Change 3 blade prop pitch. Bigger prop = bigger topend. Smaller prop gives you the hole shot. I run a 11 for the shot and a 12 to squeeze a little more out the top.
IMO. 4 blades shouldn't be faster, but give better results outta the hole. Less cavitation too while turning. Possibiy better fuel economy. Old warn out props don't help. I reckon a new 3 would be bette for you
That's what I thought maybe with a higher hp motor you could tell the difference more. I will be putting a brand new 40hp on the boat in 6 months so not overly worried haha
More blades on a prop actually makes it slower and it's has to do with physics. If you want more power with more blades, they have to be shorter. Think like a airplane turbine blades, they have alot, but they are much shorter, and that's because what ever medium you wish to pass the blade, you must make sure that the same amount you pushing away must be able to fill up the empty space with the suck of 1 bar or you reach vaccum and that's it, nothing happens. Don't have a motor and you want to test it at home. Do you have a ceiling fan with 4 blades or more. Try to remove all blades and only leave 2 on the opposite against each other. The unbalance will occur but notice what a big difference in airflow. Low speed with 2 blades is now almost the same as high speed with 5 blades.. and it all comes down to the fan have to be able to suck the same amount of air as it push or otherwise it will counteract on it self and work very poor. The same happens in water, the prop will only cavitate with more blades. But big boats have more blades you say? Yes but they have also a different angle of attack to slice thru water more efficiency and they do it much slower also so water have the time to fill the empty space without reaching vaccum.
I also have a 25 hp that has trouble planing with passengers. Also debating a 40 but don’t want to spend the money. Also going to try prop changes first. I wish this test was a test that changed the pitches of the props instead of the blade number. I think that would’ve been a better test for you . I’ll lyk how my test goes. 13 foot whaler with 11.25 pitch on 3 blade prop. I know I also have range to go because I’m WOT at 5 k rpm’s and 22 mph and I should be 5600 at WOP at least. Remember the 4 blade prop will take more power to spin and therefor not allow the motor to rev out and reach its rated HP I’m a timely manner. I thought I needed a 4 blade prop for more torque but after doing a ton of research I think my best bet is to keep 3 blade and lower the pitch and get my rpm’s up sooner in the power band and like I said I have 1000 rpm’s to play with up top.( although I’ll probably only push it to 5700 WOP )
Thanks mate!! I could of definitely done a few props to compare! But unfortunately this was the only option they had at the shop. But was still an interesting test! I was surprised the difference it makes!! Goodluck finding the perfect prop mate!!
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Change 3 blade prop pitch. Bigger prop = bigger topend. Smaller prop gives you the hole shot. I run a 11 for the shot and a 12 to squeeze a little more out the top.
IMO. 4 blades shouldn't be faster, but give better results outta the hole. Less cavitation too while turning. Possibiy better fuel economy. Old warn out props don't help. I reckon a new 3 would be bette for you
That's what I thought maybe with a higher hp motor you could tell the difference more. I will be putting a brand new 40hp on the boat in 6 months so not overly worried haha
More blades on a prop actually makes it slower and it's has to do with physics. If you want more power with more blades, they have to be shorter. Think like a airplane turbine blades, they have alot, but they are much shorter, and that's because what ever medium you wish to pass the blade, you must make sure that the same amount you pushing away must be able to fill up the empty space with the suck of 1 bar or you reach vaccum and that's it, nothing happens. Don't have a motor and you want to test it at home. Do you have a ceiling fan with 4 blades or more. Try to remove all blades and only leave 2 on the opposite against each other. The unbalance will occur but notice what a big difference in airflow. Low speed with 2 blades is now almost the same as high speed with 5 blades.. and it all comes down to the fan have to be able to suck the same amount of air as it push or otherwise it will counteract on it self and work very poor. The same happens in water, the prop will only cavitate with more blades. But big boats have more blades you say? Yes but they have also a different angle of attack to slice thru water more efficiency and they do it much slower also so water have the time to fill the empty space without reaching vaccum.
Wow mate! Very informative and interesting!! Makes sense!! Thanks so much mate!! Massive help!!
I also have a 25 hp that has trouble planing with passengers. Also debating a 40 but don’t want to spend the money. Also going to try prop changes first. I wish this test was a test that changed the pitches of the props instead of the blade number. I think that would’ve been a better test for you . I’ll lyk how my test goes. 13 foot whaler with 11.25 pitch on 3 blade prop. I know I also have range to go because I’m WOT at 5 k rpm’s and 22 mph and I should be 5600 at WOP at least. Remember the 4 blade prop will take more power to spin and therefor not allow the motor to rev out and reach its rated HP I’m a timely manner. I thought I needed a 4 blade prop for more torque but after doing a ton of research I think my best bet is to keep 3 blade and lower the pitch and get my rpm’s up sooner in the power band and like I said I have 1000 rpm’s to play with up top.( although I’ll probably only push it to 5700 WOP )
Thanks mate!! I could of definitely done a few props to compare! But unfortunately this was the only option they had at the shop. But was still an interesting test! I was surprised the difference it makes!! Goodluck finding the perfect prop mate!!
You’ll probably know it, the “ pitch “ has a bit too do with speed.
Most definitely! It's crazy the difference it makes having the right prop!!
Pitch down