See full version: Boat Propeller Fit Guide
If you're buying a new propeller for your boat, you may simply need a replacement for a prop you damaged, you may be trying to address a performance issue (e.g. being under or over propped) or you may simply want to gain better fuel economy. Whichever the case, we can help you find the right propeller for your needs.
Propellers are commonly available in either three or four blades. more
Propellers are comprised of different materials, shapes, and sizes to suit the broad spectrum of use cases and conditions in which a propeller must perform. If you're looking to change your propeller for one that better suits your need, it will help to learn a little about propeller construction, types of propellers, materials used in constructing propellers, as well as the number of blades on a propeller, and other blade performance factors.
On the other hand, a higher pitch affects your boat performance by delivering greater top speeds, but at the expense of your acceleration or hole-shot. (Warning: lower-horsepower engines can bog down if fitted with a propeller with too high of a pitch. This can cause heavy wear on the internal engine parts, who will have trouble keeping up). more
When purchasing a new marine propeller , it is important to know what propeller pitch and diameter would best suit your boat. With this guide, you will learn not only what propeller pitch and diameter are, but how they affect your boat’s performance.
If you’re changing the pitch on a recreational boat, there’s a rule of thumb often used that says each inch of pitch is generally worth 150 – 200 rpm. Lowering the pitch increases rpm and vice versa. So for instance, if you were to lower from a 23-pitch to a 21-pitch propeller, you’ll increase engine RPM by about 400 revolutions. more
What’s most important is your performance goals. If you load your boat with heavy gear, you might need a lower pitch to get your boat moving from a standstill. If not weighed down by anything, you may just want a higher top speed, and in that case, a higher pitch is what you’d want. here
When driving forward you can easily compensate for prop walk with your rudder, so you hardly notice it. In reverse your rudder is much less effective, so prop walk is more obvious and more difficult to control. To compensate, or to take advantage of it, you must anticipate its force and direction.
If you cannot see your prop or shaft, observe the direction of the prop’s wash on the water’s surface. Put your engine in reverse at one-quarter throttle while tied to a dock and look over the stern quarters. If you see prop wash on the starboard side, then your propeller is right-handed and your stern will walk to port. If the wash is on the port side, your prop is left-handed and will kick the stern to starboard. You can conduct the same test underway by bringing your boat to a full stop dead downwind or in calm conditions. Shift to reverse, give her a few seconds burst of throttle, and observe whether the stern moves to port or starboard. more
This technique will spin most boats in their own length, plus a little—a bit less for fin-keel boats, more for longer keels. It only works pivoting to starboard with a right-handed prop or to port with a left-handed prop. If you try to pivot the wrong way, prop walk will work against you each time you power up in reverse, slowing or even thwarting the turn. If you must turn a right-hand prop boat 90 degrees to port in tight quarters, you’ll probably be better off spinning her 270 degrees to starboard. Practice pivoting your boat in open water until you get the feel of it.
Keep repeating this sequence, alternating throttle bursts in forward and reverse, until the boat has spun to the desired heading. Throughout this maneuver, keep the helm turned to starboard—the rudder should have no effect in reverse, since the boat’s not making sternway—and always spend a moment in neutral between each shift to spare the transmission any sudden jolts. [links]
All the ones I've seen, the outward drives are counter rotating, while the center will either spin right or left. here
It says the two outside motors turn the same direction and the middle one is the one that turns different. They talk about how to maneuver in tight spots by either putting the two outside drives in neutral and using only the middle motor to turn. Or the other option was to put the middle motor in neutral and use both outside motors one forward and one reverse for a tight turn. Maybe I read it wrong. Who knows.
I was checking out some pictures of boats with triple motors and was curious how they setup the props for those. I know on twins they have a prop for the right and a prop for the left to keep the boat level. Can't really do that with triples so doesn't the boat lean one way or the other? :headscratch:
No you read it right, but I have never seen a setup like that, where the outward props rotate the same direction and the center prop counter rotates.
In a docking scenario you leave the center drive in neutral, using the outer drives to maneuver the boat.