Lifting Keel .. falure and repair

Hi All,
This is a long saga, So I will attack it over a few instalments,
The keel is a swing type, Pivoted at the front/top and lifted by what can best be described as an oversize Brass nut and S/S bolt. The nut is attached to the keel at a point about 18" behind the pivot point While the bolt is fixed in the boat on the rear end of the table... as you wind the bolt in it raises the keel,as you wind it out it lowers it.. Simple..
We have Animal 5 years now and the nut has failed 3 times, So obviously there is an issue.
Falure of the nut is the most common problem and causes the keel to drop to the down position and not be able to be lifted..
We Think The original nut was to soft, It appears that there is now a modified one which we have fitted(it also has a modified price ) Remember the only time the nut is not under stress is when the keel is fully lowered.
We feel it is VERY IMPORTANT not to overtighten when in the fully up position as this puts huge aditional pressure on the nut. On The 260 It is exactly 100 turns to lift so the last 2 or 3 are done very carefully and when the pressure comes on it is given a 1/4 turn back
There is a metal bracket covering the lifting mech.in the salon,We have removed this so that if we touch ground the unit simply pushes up through the table rather than trying to support the weight of the boat on the nut.. We have done this several times and it is very obvious to the helm as the unit is in clear line of sight.. Touching bottom in sandy areas can be very gentle but as the boat comes upright ie tacking the full weight comes onto the keel nut and can cause the boat to fail to tack or strip the nut..
Lots More To Follow.. Iain