Do you need a prop size calculator? Learn how to measure propeller diameter and calculate both hub length and blade length to get the total length of the propeller
Please be aware:
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Unlike the general perception, even as little as 8-10 mm of free space between propeller and hull will be fine. However, this of course depends on the specific hull shape and less clearence will normally increase propulsion noise.
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Due to the nature of the propeller construction, folding blades are positioned further aft than a fixed propeller (see hub length) and thereby leave more space between shaft and hull.
Hub length, ISO standard shaft
Hub length (A), 2-blade
22 mm shaft, 1:10 taper = 88 mm
25 mm shaft, 1:10 taper = 110 mm
30 mm shaft, 1:10 taper = 130 mm
30 - 2A mm shaft 1:10 = 137.50 mm
35 - 2A mm shaft 1:10 = 147.50 mm
40 - 2A mm shaft 1:10 = 157.50 mm
Hub length (A), 3-blade up to 23"
25 mm shaft, 1:10 taper = 120 mm
30 mm shaft, 1:10 taper = 136 mm
35 mm shaft, 1:10 taper = 146 mm
40 mm shaft, 1:10 taper = 156 mm
45 mm shaft, 1:10 taper = 196 mm
Hub length (A), 3-blade >22" and 4-blade
35 mm shaft, 1:10 taper = 148 mm
40 mm shaft, 1:10 taper = 157 mm
45 mm shaft, 1:10 taper = 196 mm
50 mm shaft, 1:10 taper = 206 mm
Hub length, SAE standard shaft
Hub length (A), 2-blade
3/4" shaft, 1:16 taper = 100 mm
7/8" shaft, 1:16 taper = 115 mm
1" shaft, 1:16 taper = 130 mm
1 1/8" shaft, 1:16 taper = 142 mm
1 1/4" shaft, 1:16 taper = 157 mm
Hub length (A), 3-blade up to 23"
1" shaft, 1:16 taper = 136 mm
1 1/8 shaft, 1:16 taper = 146 mm
1 1/4" shaft, 1:16 taper = 156 mm
1 1/2" shaft, 1:16 taper = 194 mm
1 3/8" shaft, 1:16 taper = 177 mm
1 3/4" shaft, 1:16 taper = 210 mm
Hub length (A), 3-blade >22" and 4-blade
1 1/2" shaft, 1:16 taper = 202 mm
1 3/4" shaft, 1:16 taper = 210 mm
2" shaft, 1:16 taper = 275 mm
Hub length, IMP standard shaft
Hub length (A), 2-blade
3/4" shaft, 1:12 taper = 96,5 mm
1" shaft, 1:12 taper = 110 mm
1 1/4" shaft, 1:12 taper = 129 mm
Hub length (A), 3-blade up to 23"
1" shaft, 1:12 taper = 116 mm
1 1/4" shaft, 1:12 taper = 136 mm
1 1/8 shaft, 1:12 taper = 120 mm
Hub length (A), 3-blade >22" and 4-blade
1 3/4 shaft, 1:12 taper = 196 mm
Hub length (A), saildrive
Hub for 2-blade propeller = 135 mm
Hub for 3-blade propelelr = 135 mm
Blade length (B)
2-blade propeller:
12" = 139 mm
13" = 152 mm
14" = 165 mm
15" = 177 mm
16" = 190 mm
17" = 203 mm
18" = 215 mm
19" = 228 mm
20" = 241mm
3-blade propeller:
14" = 151 mm
15" = 163 mm
16" = 176 mm
17" = 189 mm
18" = 202 mm
19" = 216 mm
20" = 227 mm
22" = 250 mm
23" = 262 mm
4-blade propeller
25" = 275 mm
Propeller diameter
12" = 305 mm
13" = 330 mm
14" = 356 mm
15" = 381 mm
16" = 406 mm
17" = 432 mm
18" = 457 mm
19" = 485 mm
20" = 508 mm
21" = 533 mm
22" = 559 mm
23" = 585 mm
24" = 610 mm (3-blade propeller)
24" = 625 mm (4-blade propeller)
26" = 660 mm