Overview
ISO 8845:1994 specifies dimensional requirements to ensure interchangeability of propeller bosses (hubs) and propeller shaft ends for small craft with inboard engines. The standard covers shafts and mating bosses with a 1:16 taper in the nominal shaft diameter range 20 mm to 160 mm, and is intended for new metric-dimension propeller shafts used in recreational and commercial small craft.
Key Topics
- Scope and purpose: Defines dimensions and designation rules to permit interchangeability between propellers and shafts manufactured to the standard.
- Taper geometry: Standardizes a 1:16 conical taper for shaft ends and corresponding bosses; cone tolerances follow ISO 1947.
- Diameter range: Nominal diameters from 20 mm to 160 mm (some diameters listed as non-preferred).
- Dimensional data: Detailed dimensions and tolerances are given in the standard’s figure and Table 1 (shaft small diameter, boss large diameter, thread lengths, bores, chamfers, etc.).
- Tolerances: Shaft and boss tolerances are specified by the table and by referenced standards (cone tolerances per ISO 1947; key tolerances per ISO/R 773).
- Keyways and keys: Key and keyway geometry follows ISO/R 773; the taper accommodates a key to transmit full propeller torque while allowing disassembly.
- Threads and propeller nut engagement: Propeller locknuts and shaft threads are metric fine screw threads. Thread length requirements: thread length Z4 ≥ thread diameter dz, and the portion of thread engaged by the propeller nut must be not less than 80% of that thread length (figure notes indicate minimum engagement details).
- Construction details: Optional features (safety pin-holes, centring points, corner radii, thread undercuts) are left to manufacturers; only dimensions in the table are essential to interchangeability.
- Designation: Parts conforming to this standard are designated by reference and nominal diameter (example: “Propeller boss ISO 8845 - 80”).
Applications
ISO 8845:1994 is useful for:
- Marine propeller manufacturers and shaft suppliers specifying mating components.
- Shipyards, boatbuilders and repair yards ensuring parts interchangeability for inboard-engined small craft.
- Naval architects and marine engineers specifying shaft-to-propeller connections.
- Spare-parts procurement, maintenance teams and marine surveyors verifying conformity and fit.
The standard supports consistent retrofit, replacement and cross-sourcing of propellers and shafts within the specified metric range.
Related Standards
- ISO 1947 - cone tolerances for conical workpieces (referenced for cone tolerance classes).
- ISO/R 773 - rectangular/square keys and keyways (dimensions and tolerances).
- ISO 4566:1992 - earlier work on propeller shaft taper (7:70 taper) referenced in the bibliography.
- SAE J755 - may be appropriate for inch-based or legacy replacement shafts.
Keywords: ISO 8845, small craft, propeller shaft ends, propeller bosses, 1:16 taper, interchangeability, shaft diameters 20–160 mm, metric threads, tolerances.