I’ve got a 15 degree pitch prop on my 150 verado. To me it doesn’t seem like the best prop for the boat. Any advice?
'08 Sea Pro 206cc
150 Verado
I don’t know it all… but, I figured I’d lay out a primer and see if there are any experts that can correct me where I’m getting it wrong and/or fill in the gaps… like blade shape.
First coarse measure… do you have ‘enough’ prop? You’re motor will have a specified range of rpms for WOT. My old Johnson should fall between 4800-5600 (or, something like that). If, at WOT with a typical load, you are over the range specified for your motor, you are under prop’d, your motor is spinning to easily. If you don’t spin the minimum rpms, you’re over prop’d.
What determines the ‘amount’ of prop? A combination of diameter, pitch, number of blades, and blade shape.
Your diameter is limited by the space between the prop shaft and the underside of your anti-ventilation plate. Motor and prop manufacturers will usually recommend a few (2 or 3) diameters that are generally useful on your boat/motor combination. For nearly all applications, go with the default.
Then there is pitch ( can be thought of as how far the prop, by itself, would move straight forward if spun one revolution in jello). The more pitch, the farther the motor is trying to push the boat with each turn of the prop. Using one pitch vs. another will effect things like how quickly the boat comes up on a plane and top end speed. Reducing pitch is like using a lower gear and you’ll come out of the water faster. Using more pitch will be like a higher gear. You’ll come out of the water slower, but, would theoretically have a higher max speed. This is intuitively obvious when you think about a car. If you start off in first gear, you get going easily, but, you have a very low top speed. If in a higher gear, getting going can be much more difficult, but, once moving, you have a much higher top speed.
If you think you have the correct diameter, if you aren’t turning enough WOT rpms, then you have to much pitch. If you are turning to many WOT rpms, you don’t have enough pitch. If you are coming out of the hole fine and are turning
Take it out and record speed every 500 rpms ,once you get it on plane, until wot. That will give you a lot of information, including prop slip.
Until you do that, you’re just taking blind guesses. And you’ll need to know what your diameter is, and either al or ss.