Hi , we own a 1980 Maramu and had similar concerns before taking her offshore- before we went I asked many boat builders and all the experts re-assured us that the build quality , redundancy in the number of bolts and the stub keel design make it a non-issue for the Maramu. They further placated us in that there has never been any known catastrophic failure ( to date ) of an Amel's keel bolts, to their knowledge.
We made the 14 day non stop passage however the condition of the keel bolts was always in the back of my mind.
When we lifted the engine for reconditioning, we had good access to the deep bilge and could view the one bolt head .. like new . Then later when we cleaned the water tank we had access to the other bolts , they also looked in pristine condition.
In the saloon in front of the saloon table there is an easily accessible access opening for the tank , where you have the opportunity to easily view the bolts in that section .
Lastly, I was advised not to Pull a bolt for testing , as I would do more damage then good and as there did not appear to be any issues with any of them to leave well alone .
We are happy and sleep easy.
Trust the above is helpful.