Structual modifications and implications

[Rokraider]

Another thread piqued my interest with regards to modifying your boat structually and the possible implications of doing so.
I know little about the CE process on boats, but assume that boat design and composition must enter in to it, which will include structual integrity?

What started this question is Modifications that have been carried out on a RIB I bought.

I have been rebuilding a PAC 22 that has been fitted with a Sabre 250 BHP 6 cylinder engine and Hamilton Jetdrive. Because the engine is quite a bit longer that the original 4 cylinder, whoever did the modifications chopped out the entire bulkhead at the front of the engine to create some space. It appeared to have been done fairly sensibly until I pulled the deck off. Turns out that there was nothing of any substance to replace the missing section, leaving the hull severely weakened right at the point where it needed it most.
I have now fabricated a strong bulkhead that ties everything together again and has put stiffness back in the hull.
I do not know the history of my RIB so do not know who carried out the modifications, but was wondering about the implications with regards to safety, insurance etc if the hull had failed, say after a hard landing. Would the insurance company walk away from a claim when they find it has been modified badly?

I was also mulling over the position where a company has carried out structual modifications to a new hull that has previously been issued with a CE test certificate as designed. If the modifications have weakened the hull design, presumably it would no longer pass a CE test?

[beamishken]

I think modifications to boats are fairly common and generally accepted but id assume in the event of a failure if the quality was poor and led to an insurance claim then insurers would not pay out which seems logical
I re-engined a searay sundancer several years ago took out a pair of 165hp 4 cyl diesels and fitted a pair of 300hp diesels (which I got at a very good price) however the biggest engines searay fitted to the hull was a pair of 260hp petrols so my plan was to over engine the boat by 80hp so my dilemma was do I go ahead or find a pair of (probably more expensive) smaller engines
The remedy came in the form of a surveyor's report which confirmed the installation was up to scratch and the boats safety and performance wouldnt be detrimentally affected
Id say small mods which are obviously sound should be fine but anything major that makes you think "is that ok" then get a professional surveyor's report to confirm its ok you ate then covered