Loose Helm Seat Base: 1987 V20

[DiverDux]

We (my brother and I) own an 87 V20 cuddy IO. The base to the pedestal seat at the helm is loose. It can be tightened down, but it loosens again in a short period of time.

My brother lifted the floor over the gas tank, hoping to gain access to the area below the base. The fix was to put a plate below the base and put bolts and nylanuts hoping that that would remedy the problem. What he found was 2x2 wood surrounding the outside top edge of the tank and spray-in foam filling any voids.

He promptly replaced the floor deciding to research the repair before tearing anything out.

Suggestions? Is there any other access to this area? Has anyone dealt with this issue? If so, what did you do?

Thanks in advance!