It is quite normal for an insurer to request a periodic survey, usually on boats that have reached say 20 or 30 years of age, but also perhaps if the boat has been extensively modified or if there is a request to increase the insured value by a significant amount.
Clearly the underwriter is concerned to quantify their risk, and wants to be sure that there have been no unsuitable modifications or significant deterioration or lack of maintenance that would excessively increase their risk. They will also usually want an independent professional opinion on the value. This latter aspect could be addressed by a professional yacht broker, but the technical side falls normally to a qualified surveyor, the most usual and acceptable UK qualification being membership of the Yacht Designers & Surveyors Association (YDSA)*, but UK underwriters may well also recognise surveyors of other nationalities with appropriate national qualifications and the ability to report in English (assuming of course that you are dealing with a UK insurer).
The technical side of the survey will be concerned with overall structural condition, stern gear, skin fittings etc. plus safety aspects such as gas and other fuel installations, fire fighting provisions etc. but will not address cosmetic matters other than as pertinent to valuation, so it would not be as extensive a survey as one would want for purchase purposes. On a GRP boat, for example, the insurance survey will not major on aspects such as osmotic degradation in the laminate except where this is so extensive that it poses a structural risk, but obviously as a buyer you would want a more detailed opinion. In short, the underwriters want professional affirmation that the boat is unlikely to sink, roll over, blow up or otherwise injure people medium term.
*In the Netherlands, HISWA. [Ed]
Original by Balliol Fowden, Oct 2015