Hi Hannu,
Thanks for your input. I put 3kN in as an max estimate and the calcs showed 4.04kN for dynamic axial load rating for the bearing
Looking at a 10m sailboat with locked 3 blade 14" prop giving a drag of about 45kg (100lbf) at 7 knots, and my 26ft boat with long keel protecting the prop and max bollard pull of around 150lbf,with max running thrust of around 100lbf - then it seems the safety factors are OK. I appreciate the difference between dynamic and shock load as you suggest. My prop is also in an aperture and shielded further by the deadwood.
I use a flex coupling between prop and motor shaft and flex isolation mounts for the motor mounting, so short of lots of R & D money I think I'm safe, if not completely without risk.
I suppose my arrangement is no different to the original 10bhp Volvo motor, where the gearbox bearing took these loads. I never did find out that bearing rating.
Real world testing so far has not shown up any problems. I also assume direct drive motors like the Elco take the same approach but I don't know their bearing arrangement?
John
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