Teague’s Take: Propeller Questions
10-16-2015, 01:58 PM
#1
Teague’s Take: Propeller Questions
During the 40 years that I’ve been a part of the marine industry, I couldn’t even begin to count how many questions I’ve answered via phone calls, emails, at events or in person at Teague Custom Marine in Valencia, Calif. Whether the subject is engines, drives, props, exhaust, oil, controls, overall setup, winterizing or even driving advice, nothing is off limits.
And that doesn’t include the several hundred questions I’ve answered in publications over the last three decades on everything from carburetors and gauges to step-bottom design and fuel-related concerns regarding ethanol and nitrous oxide.
I’m not sure if I’ll answer questions or pull some of my all-time favorites like I did for this column in every issue, but I would like to bring back the Q&A in some form and welcome any questions you have. Dedicating a column to specific subjects, i.e. hydraulic steering, trim tabs, water pumps and more, should be pretty informative and fun.
IN OR OUT?
Q: I have a 2000 Formula 353 FAS3Tech with Mercury Racing HP500EFI engines. I’m spinning 30”-pitch Bravo One four-blade propellers. I plan on swapping props to spin them in. My goal is to improve bowrise and increase performance teague’s TAKE in terms of throttle response and top-end speed. What do you think I can expect?
A: You’re likely to gain some top-end speed in your FAS3Tech by turning the propellers inward, although the gains may not be worth the possible deterioration of handling characteristics that you may experience.
Generally speaking, the boat will come on plane faster with the propellers turning outward. With the outward rotation, there’s usually more transom lift, which helps to reduce bowrise. This is especially true with side-by-side big-block installations with all the weight aft on boats 35 feet or shorter.
If your boat has any tendency to chine walk, the additional bowlift realized by
turning the propellers inward will probably have an effect on the intensity for better or
worse. In some cases, control is improved. But more often the result is a boat that is a little more difficult to drive at top speed.
Another drawback of rotating your propellers inward is the effect that it has on how the boat handles around the docks. If your propellers are rotating in, you may find that you have to steer the boat in addition to shifting, especially if wind or a current are present.
PROBABLY NOT
Q: I have a 1990 Advantage 21SR with a stock 454 Magnum, a Bravo One drive and a 23”-pitch, three-blade Mirage propeller. I believe the horsepower is 365. I can get the boat to a top speed of 65 mph. Would a higher-pitch, four-blade prop give me more top speed without taking too much performance from my bottom-end?
A: It is likely that the X dimension on your Advantage is set at a pretty conservative level, which means that the prop is running fairly deep. If the boat goes on plane well with the three-blade Mirage propeller, chances are that a higher-pitch, four-blade propeller won’t provide any benefits, especially for top speed. With your smaller V-bottom, the more hooked up four-blade propeller may cause the boat to lean in the opposite direction of the propeller rotation during acceleration, and the other way during deceleration. A four-blade will probably be more efficient in the midrange, but that is about it.
And that doesn’t include the several hundred questions I’ve answered in publications over the last three decades on everything from carburetors and gauges to step-bottom design and fuel-related concerns regarding ethanol and nitrous oxide.
I’m not sure if I’ll answer questions or pull some of my all-time favorites like I did for this column in every issue, but I would like to bring back the Q&A in some form and welcome any questions you have. Dedicating a column to specific subjects, i.e. hydraulic steering, trim tabs, water pumps and more, should be pretty informative and fun.
IN OR OUT?
Q: I have a 2000 Formula 353 FAS3Tech with Mercury Racing HP500EFI engines. I’m spinning 30”-pitch Bravo One four-blade propellers. I plan on swapping props to spin them in. My goal is to improve bowrise and increase performance teague’s TAKE in terms of throttle response and top-end speed. What do you think I can expect?
A: You’re likely to gain some top-end speed in your FAS3Tech by turning the propellers inward, although the gains may not be worth the possible deterioration of handling characteristics that you may experience.
Generally speaking, the boat will come on plane faster with the propellers turning outward. With the outward rotation, there’s usually more transom lift, which helps to reduce bowrise. This is especially true with side-by-side big-block installations with all the weight aft on boats 35 feet or shorter.
If your boat has any tendency to chine walk, the additional bowlift realized by
turning the propellers inward will probably have an effect on the intensity for better or
worse. In some cases, control is improved. But more often the result is a boat that is a little more difficult to drive at top speed.
Another drawback of rotating your propellers inward is the effect that it has on how the boat handles around the docks. If your propellers are rotating in, you may find that you have to steer the boat in addition to shifting, especially if wind or a current are present.
PROBABLY NOT
Q: I have a 1990 Advantage 21SR with a stock 454 Magnum, a Bravo One drive and a 23”-pitch, three-blade Mirage propeller. I believe the horsepower is 365. I can get the boat to a top speed of 65 mph. Would a higher-pitch, four-blade prop give me more top speed without taking too much performance from my bottom-end?
A: It is likely that the X dimension on your Advantage is set at a pretty conservative level, which means that the prop is running fairly deep. If the boat goes on plane well with the three-blade Mirage propeller, chances are that a higher-pitch, four-blade propeller won’t provide any benefits, especially for top speed. With your smaller V-bottom, the more hooked up four-blade propeller may cause the boat to lean in the opposite direction of the propeller rotation during acceleration, and the other way during deceleration. A four-blade will probably be more efficient in the midrange, but that is about it.
