Prop and shaft balance

[jasavo]

I have a new boat, well a 20 year old new boat, which has been laid up for the last 18 months. The opportunity exists to take out the propellor shaft and prop and therefore I am thinking of doing this and having it balanced. The previous owner says he was not aware of any bad vibrations. So should I go ahead and have it balanced just because the opportunity exists?

I've made a few enquires here in Cornwall and the respones I have received, is well we would have to send it away to Wales and do not know what the cost would be! Any recommendations for companies on the south coast who do this type of work and idea of cost for a folding two blade prop and shaft from a 30' boat? I believe I have seen a recommendation on this forum for a place in Poole, but can't find it again!

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[longjohnsilver]

Yes well worth doing, try C & O engineering in Newton Abbot, not sure if they do folding props.

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[Plum]

Taking the shaft out for inspection is a good idea, but I see no reason to have it balanced unless you know you have a problem or your shaft rotates in excess of 2500 rpm. The only reason a conventional boat prop, shaft and coupling can go out of ballance is if the prop gets damaged. If the prop apears undamaged then don't bother, if it has visible damage then you need to get this fixed or buy a new prop. Check also that the prop has a "ring" to it which should indicate crack or corrosion damage. You are more likely to get vibrations from aged flexible mounts or flexible couplings or from a missaligned shaft to gearbox, so your time will be better spent checking these. (Check misalignment after launching)

Hope this helps.

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[Birdseye]

I agree entirely. Unless the shaft is bent, shaft balance will not be a problem. if its bent, balancing wont help. and in view of previous owners comments, particularly if you asked him after you bought, I would concentrate on other things. stern gland, bearing, rudder pintles, sea cocks, through hulls. etc.

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[charles_reed]

Don't waste your time, money or energy - unbalanced shafts and props are seldom, if ever a problem on anything but a high-speed train.

Far better check cutless bearing area for wear and prop for soundness as well as propshaft seal.

definitely have alignment checked after boat is back in the water.

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