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A ship's propeller is possibly the most essential component of a motorboat. It requires a lot of attention, both by the naval architect and by the propeller manufacturer. "Specialists", who are able to tell you "off the cuff" what type of propeller your boat requires, simply do not exist. TechProMax makes good use of an especially developed computer program, which ensures the determination of the exactly right propeller for your boat, with the aid of some (correct) information, which we require from you.

What are the most important demands made upon a ship's propeller?
If you bear in mind that a propeller is often rotating at 2.000 r.p.m. (which is more than 30 revolutions per second!), you will appreciate that a good ship's propeller should be well-balanced. A difficult and time-consuming job, but an absolute must" nonetheless.

In order to achieve the best performance and to prevent vibrations, it is extremely important to ensure that the pitch of each blade s identical and also that the distance between the blades does not vary. Again, this requires great manufacturing precision.

"Bronze" is the common denominated a great variety of alloys. TechProMax propellers are made of manganese bronze, an extremely resilient, yet very flexible material. By virtue of their material specifications, TechProMax propellers, when damaged, can nearly always be repaired. The choice of a good (TechProMax) propeller combining all qualities mentioned above, is therefore of utmost importance! The diameter and the pitch of ship's propellers are early always given in inches (1" = 25.4 mm). All propellers with dimensions which deviate from standard sizes are available with a delivery time of 10 to 12 weeks.

The blade area
In order to specify the correct propeller, the propeller specialist must first of all determine the required Fa/F ratio. Each propeller has a fixed Fa/F ratio. This means the total area of the propeller circle (F) in comparison to the surface area (stretched and developed) of all blades together (Fa). The choice of the Fa/F ratio is dependent on the shape of the underwater section and the speed of the boat in question.

Top quality zinc-plated measuring device for exact determination of the diameter and pitch of marine
propellers up to a maximum diameter of 560 mm and a maximum shaft hole diameter of 50 mm (for pitch
measuring only: suitable for propellers with maximum diameter of up to 800 mm).

Standard taper of shaft holes of TechProMax propellers (1:10). Dimensions according to ISO 4566

Propeller diameter

Smallest diameter Hub length Keyway
propeller P3B
propeller P3C
propeller P4E
25" and

25" and

25 mm
30 mm
35 mm
40 mm
45 mm
50 mm
22 mm
26 mm
30 mm
34 mm
38 mm
60 mm
80 mm
90 mm
100 mm
110 mm
120 mm
8 mm
8 mm
10 mm
12 mm
14 mm
14 mm

TechProMax repairs ship's propellers with diameters between 12" and 24" (30-60 cm)

3-bladed propeller
Type P3B
Suited for "displacement craft with speeds of up to 10 knots.
3-bladed propeller
Type P3C
Suited to fast craft.
4-bladed propeller
Type P4E
Suited to "semi-planning" boats with speeds of more than 16 knots.

How to order?
Please give us the dimensions of the propeller's diameter and pitch, as well as the number of the blades, the sense of rotation and the dimensions of the boss and the taper, according to the sketch here below.
Tapering of the propeller shaft
All propellers in stock at TechProMax have the standard taper 1:10. This means that the difference between the largest and the smallest diameter of the tapered hole represents 10% of the length of the propeller's boss (D-d=0.1 x L).

If required, we can machine the boss to a taper of 1:12,116, etc. It takes a few days extra delivery time plus a small surcharge. (see price list)

TechProMax Dyno-Balanced Certified
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